MAINT-4532: properly detect Windows 10 in the 64bit build (only - 32bit runs in Windows 8 compatibility mode)

Drake points out that the OS X 64-bit-capable memory-query APIs recommended in
comments by some long-ago maintainer are by now themselves obsolete. He
offered this patch to update us to current macOS memory APIs.

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.

Update to build on Xcode 6.0: collection of similar const var not used warnings/errors [-Wunused-const-variable]

continued conversion to units system
made units perform type promotion correctly and preserve type in arithmetic
e.g. can now do LLVector3 in units
added typedefs for remaining common unit types, including implicits

converted many values over to units system in effort to track down
source of 0 ping

replace llinfos, lldebugs, etc with new LL_INFOS(), LL_DEBUGS(), etc.

fixed ostream precision munging in llsys

MAINT-2740 and MAINT-2672 rework after code review for 2740 fix and include 2672 fix needed for doing local integ tests

MAINT-2740 make use of OsOutputDebugString _DEBUG only to avoid interactions between Win 32-bit SEH and boost coroutine fiber stack handling

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

BUG-2707 eliminate debug message and memory dump from FrameWatcher, which appears to be going off on login for some

cleaning up build
moved most includes of windows.h to llwin32headers.h to disable min/max macros, etc
streamlined Time class and consolidated functionality in BlockTimer class
llfasttimer is no longer included via llstring.h, so had to add it manually in several places

MAINT-1815 Fix for excessive memory usage in Mayfair.  Disable tcmalloc.  Disable private memory pools.  Make viewer large address aware on windows.

Reviewed by Kelly

EXP-1525 FIXED Potential fix for a crash at shutdown: added some error handling to saving inventory cache.

storm-1729: ensure that cpu id has no leading or trailing spaces for ease of comparison and formatting

* Mac memory stats now extracted from proper system calls.

Reviewed by Nat Linden.