~LLEventPumps() deletes every LLEventPump instance it created itself. However,
many classes themselves contain LLEventPump subclass instances. These are
registered with LLEventPumps without it managing their lifespan.

But LLEventPump::reset() frees the LLStandardSignal aka
boost::signals2::signal instance owned by the LLEventPump, perforce
disconnecting all current listeners and disabling the LLEventPump. Even though
the instance still exists, if someone subsequently calls post(), nothing will
happen -- which is better than control trying to reach a method of a deleted
object.

Having a map from std::string to a factory function returning LLEventPump* is
a cool idea, especially since you could statically populate such a map with
string literals and little lambdas.

Unfortunately, static initialization of any data is a bad idea when control
can reach consuming code before that module's static data are constructed.

Since LLEventPumps is already an LLSingleton, it's simple enough to make its
map non-static and initialize it in the constructor.

But another recent static factory-function map was introduced in
llleaplistener.cpp to support the LLLeapListener::newpump() operation. That
involves no LLSingletons.

Introduce LLEventPumps::make(name, tweak, type) to instantiate an LLEventPump
subclass of the specified type with specified (name, tweak) parameters.
Instances returned by make() are owned by LLEventPumps, as with obtain().
Introduce LLEventPumps::BadType exception for when the type string isn't
recognized.

LLEventPumps::obtain() can then simply call make() when the specified instance
name doesn't already exist. The configuration data used internally by obtain()
becomes { string instance name, string subclass name }. Although this too is
currently initialized in the LLEventPumps constructor, migrating it to a
configuration file would now be far more straightforward than before.

LLLeapListener::newpump(), too, can call LLEventPumps::make() with the
caller-specified type string. This eliminates that static factory map.
newpump() must catch BadType and report the error back to its invoker.

Given that the LLEventPump subclass instances returned by make() are owned by
LLEventPumps rather than LLLeapListener, there is no further need for the
LLLeapListener::mEventPumps ptr_map, which was used only to manage lifetime.
Also remove LLLeapListener's "killpump" operation since LLEventPumps provides
no corresponding functionality.

No one uses LLEventQueue to defer posted events until the next mainloop tick
-- and with LLCoros moving to Boost.Fiber, cross-coroutine event posting works
that way anyway, making LLEventQueue pretty unnecessary.

The static RegisterFlush instance in llevents.cpp was used to call
LLEventPumps::flush() once per mainloop tick, which in turn called flush() on
every registered LLEventPump. But the only reason for that mechanism was to
support LLEventQueue. In fact, when LLEventMailDrop overrode its flush()
method for something quite different, it was startling to find that the new
flush() override was being called once per frame -- which caused at least one
fairly mysterious bug. Remove RegisterFlush. Both LLEventPumps::flush() and
LLEventPump::flush() remain for now, though intended usage is unclear.

Eliminating LLEventQueue means we must at least repurpose
LLEventPumps::mQueueNames, a map intended to make LLEventPumps::obtain()
instantiate an LLEventQueue rather than the default LLEventPump. Replace it
with mFactories, a map from desired instance name to a callable returning
LLEventPump*. New map initialization syntax plus lambda support allows us to
populate that map at compile time with little lambdas returning the correct
subclass instance.

Similarly, LLLeapListener::newpump() used to check the ["type"] entry in the
LLSD request specifically for "LLEventQueue". Introduce another such map in
llleaplistener.cpp for potential future extensibility.

Eliminate the LLEventQueue-specific test.

Overriding virtual LLEventPump::flush() for the semantic of discarding
LLEventMailDrop's queued events turns out not to be such a great idea, because
LLEventPumps::flush(), which calls every registered LLEventPump's flush()
method, is called every mainloop tick. The first time we hit a use case in
which we expected LLEventMailDrop to hold queued events across a mainloop tick,
we were baffled that they were never delivered.

Moving that logic to a separate method specific to LLEventMailDrop resolves
that problem. Naming it discard() clarifies its intended functionality.

This is like the existing reset() method, except that reset() is specifically
intended for shutdown: it disables every existing LLEventPump in such a way
that it cannot be subsequently reused. (The original idea was to disconnect
listeners in DLLs unloaded at shutdown.)

clear() forcibly disconnects all existing listeners, but leaves LLEventPumps
ready for reuse. This is useful (e.g.) for test programs to reset the state of
LLEventPumps between individual test functions.

Previously, LLEventMailDrop would send only the first queued event to a
newly-connected listener. If you wanted to flush all queued events, you'd have
to "pump" the queue by repeatedly disconnecting and reconnecting -- with no
good way to know when you'd caught up.

The new behavior makes LLEventMailDrop resemble a multi-valued future: a
rendezvous between producer and consumer that, once connected, pushes values
rather than requiring them to be pulled (as with a simple queue) -- regardless
of the relative order in which post() and listen() are called.

LLEventPump's destructor was using LLEventPumps::instance() to unregister the
LLEventPump instance from LLEventPumps. Evidently, though, there are lingering
LLEventPump instances that persist even after the LLSingletonBase::deleteAll()
call destroys the LLEventPumps LLSingleton instance. These were resurrecting
LLEventPumps -- pointlessly, since a newly-resurrected LLEventPumps instance
can have no knowledge of the LLEventPump instance! Unregistering is
unnecessary!

What we want is a reference we can bind into each LLEventPump instance that
allows us to safely test whether the LLEventPumps instance still exists.
LLHandle is exactly that. Make LLEventPumps an LLHandleProvider and bind its
LLHandle in each LLEventPump's constructor; then the destructor can unregister
only when LLEventPumps still exists.

A level of preprocessor indirection lets us later change the implementation if
desired.

This also introduces LLContinueError for exceptions which should interrupt
some part of viewer processing (e.g. the current coroutine) but should attempt
to let the viewer session proceed.

Derive all existing viewer exception classes from LLException rather than from
std::runtime_error or std::logic_error.

Use BOOST_THROW_EXCEPTION() rather than plain 'throw' to enrich the thrown
exception with source file, line number and containing function.

MAINT-6521: A compare against a static const empty string causes segfault in integration tests on Mac and Linux.  Use empty() test instead.

Initial changes for Vivox/Azumarill merge.  Lots of temporary code and conditional compile switches.   Begin switch from statemachine to coroutine.

BUG-2707 make use of OsOutputDebugString _DEBUG only on Windows to avoid throwing unhandlable exceptions in coroutines in RelWithDebInfo builds

improved LLUnit compile time errors
removed cassert in favor of llstatic_assert

It's not worth bothering to tweak reply LLSD or attempt to send it if the
incoming request has no replyKey, in effect not requesting a reply. This
supports LLEventAPI operations for which the caller might or might not care
about a reply, invoked using either send() (fire and forget) or request()
(send request, wait for response). This logic should be central, instead of
having to perform that test in every caller that cares.
The major alternative would have been to treat missing replyKey as an error
(whether LL_ERRS or exception). But since there's already a mechanism by which
an LLEventAPI operation method can stipulate its replyKey as required, at this
level we can let it be optional.

Each LLEventAPI method that generates a reply needs to extract the name of the
reply LLEventPump from the request, typically from a ["reply"] key, copy the
["reqid"] value from request to reply, locate the reply LLEventPump and send
the enriched reply object. Encapsulate in sendReply() function before we
proliferate doing all that by hand too many more times.

Replace LLEventPump's boost::scoped_ptr<LLStandardSignal> with
boost::shared_ptr. Take a local stack copy of that shared_ptr in post()
methods, and invoke the signal through that copy. This guards against scenario
in which LLEventPump gets destroyed during signal invocation. (See Jira for
details.) Re-enable Mani's test case that used to crash.
Introduce ll_template_cast<> to allow a template function to recognize a
parameter of a particular type.
Introduce LLListenerWrapper mechanism to support wrapper objects for
LLEventPump listeners. You instantiate an LLListenerWrapper subclass object
inline in the listen() call (typically with llwrap<>), passing it the real
listener, trusting it to forward the eventual call.
Introduce prototypical LLCoutListener and LLLogListener subclasses for
illustrative and diagnostic purposes. Test that LLLogListener doesn't block
recognizing LLEventTrackable base class bound into wrapped listener.

The fix deletes all LLEventPumps boost::signal objects prior to unloading any dlls.
reviewed by Nat.

RegisterFlush destructor was dereferencing a dangling reference to the mainloop EventPump which had already been destructed.

svn merge -r 121797:121853 svn+ssh://svn.lindenlab.com/svn/linden/branches/merge-event-system-7

implement the ["reqid"] convention. This convention dictates that a response
LLSD from each such API should contain a ["reqid"] key whose value echoes the
["reqid"] value, if any, in the request LLSD.
Add LLReqID support to LLAresListener's "rewriteURI" service, LLSDMessage,
LLCapabilityListener and LLXMLRPCListener.

svn merge -r113003:119136 svn+ssh://svn.lindenlab.com/svn/linden/branches/login-api/login-api-2 svn+ssh://svn.lindenlab.com/svn/linden/branches/login-api/login-api-3

svn merge -r114679:114681 svn+ssh://svn.lindenlab.com/svn/linden/branches/event-system/event-system-7 svn+ssh://svn.lindenlab.com/svn/linden/branches/event-system/event-system-8