Expand the way we set C++ flags in cmake to call out each build type explicitly

Approved-by: nat_linden <nat@lindenlab.com>

This is only transitional, until we integrate the Viewer Management Process
(soon now).

to suppress fatal warnings in Visual Studio.

Whatever we were trying to do with LLSharedLibs.cmake hasn't worked on the Mac
for a long time, and trying to fix it only digs up more problems. Skip it:
we've already worked around it.

Update the media_plugins_example CMakeLists.txt to eliminate some CMake
non-existent dependency warnings.

Evidently the Mac implementation of LLMemory::getCurrentRSS() goes back to
OS X 10.3, because there was a helpful comment of the form:

------
The API used here is not capable of dealing with 64-bit memory sizes, but is
available before 10.4.

Once we start requiring 10.4, we can use the updated API, which looks like
this:

[new current implementation]

Of course, this doesn't gain us anything unless we start building the viewer
as a 64-bit executable, since that's the only way for our memory allocation to
exceed 2^32.
------

Hey, guess what, we're building 64-bit viewers now!

Thank you, whoever thoughtfully noted that, both for calling out the issue and
sparing us the research. (The comment goes back to Subversion days, so hg
blame shows only the merge-to-release changeset.)

There were two distinct LLMemory methods getCurrentRSS() and
getWorkingSetSize(). It was pointless to have both: on Windows they were
completely redundant; on other platforms getWorkingSetSize() always returned
0. (Amusingly, though the Windows implementations both made exactly the same
GetProcessMemoryInfo() call and used exactly the same logic, the code was
different in the two -- as though the second was implemented without awareness
of the first, even though they were adjacent in the source file.)

One of the actual MAINT-6996 problems was due to the fact that
getWorkingSetSize() returned U32, where getCurrentRSS() returns U64. In other
words, getWorkingSetSize() was both useless *and* wrong. Remove it, and change
its one call to getCurrentRSS() instead.

The other culprit was that in several places, the 64-bit WorkingSetSize
returned by the Windows GetProcessMemoryInfo() call (and by getCurrentRSS())
was explicitly cast to a 32-bit data type. That works only when explicitly or
implicitly (using LLUnits type conversion) scaling the value to kilobytes or
megabytes. When the size in bytes is desired, use 64-bit types instead.

In addition to the symptoms, LLMemory was overdue for a bit of cleanup.

There was a 16K block of memory called reserveMem, the comment on which read:
"reserve 16K for out of memory error handling." Yet *nothing* was ever done
with that block! If it were going to be useful, one would think someone would
at some point explicitly free the block. In fact there was a method
freeReserve(), apparently for just that purpose -- which was never called. As
things stood, reserveMem served only to *prevent* the viewer from ever using
that chunk of memory. Remove reserveMem and the unused freeReserve().

The only function of initClass() and cleanupClass() was to allocate and free
reserveMem. Remove initClass(), cleanupClass() and the LLCommon calls to them.

In a similar vein, there was an LLMemoryInfo::getPhysicalMemoryClamped()
method that returned U32Bytes. Its job was simply to return a size in bytes
that could fit into a U32 data type, returning U32_MAX if the 64-bit value
exceeded 4GB. Eliminate that; change all its calls to getPhysicalMemoryKB()
(which getPhysicalMemoryClamped() used internally anyway). We no longer care
about any platform that cannot handle 64-bit data types.

Pull in new version of Dullahan that is built against latest version of CEF (CEF 3.3029.1611.g44e39a8 / Chromium 58.0.3029.81)

Pull in Nickyd's changes to APR and LLCEFLib (Dullahan) for MAINT-6116 Console window appears breifly for Flash sites

Add NULL macOs implementation for 'MAINT-6950 Shared media a great distance away (different region even) sometimes plays at maximum volume when entering a region or moving camera slightly.' - until we can understand how to make real mac_volume_catcher work

FIX for MAINT-6950 Shared media a great distance away (different region even) sometimes plays at maximum volume when entering a region or moving camera slightly.

of LLSafeHandle's referenced type. Using LLSingleton gives us a well-defined
time at which the "null instance" is deleted: LLSingletonBase::deleteAll().

LLWinDebug, though an LLSingleton, had (and required explicit calls to)
special init() and cleanup() methods. Kitty Barnett points out that the
cleanup() method was actually being called after LLSingletonBase::deleteAll(),
requiring resurrection of the deleted LLWinDebug, which sometimes led to
crashes. (Resurrecting deleted LLSingletons is always suspect.)

Change LLWinDebug::init() and cleanup() to the conventional initSingleton()
and cleanupSingleton() methods. This eliminates the need to make special
method calls at all. In particular, cleanupSingleton() will be called by the
existing LLSingletonBase::cleanupAll() call near viewer shutdown.

We retain the early LLWinDebug::instance() call, which implicitly initializes
the LLWinDebug instance, because evidently we want that initialized early. But
we no longer require a separate init() call.