added commented out log timestamp override for scene load performance monitoring

there are no samples during the time period.
added hasValue to SampleAccumulator so we don't print a value when we don't have
a single sample yet
added some disabled log output for scene load timing

fixed normalization assertions to work with megaprims
added is_zero() utility function
fixed unit declarations to be more clear
fixed texture cache hit rate always being 0

fast timer data now resets on login

dependency cleanup - removed a lot of unecessary includes

fixed ostream precision munging in llsys

made unit types work with ostreams
fixed timing of scene monitor recordings to better respect requested time diff

timing of scene load recording extension now guaranteed > requested time step
removed double add of recorded data
removed spam

various fixes to lltrace
start() on started recording no longer resets
fixed various instances of unit forgetfullness in lltrace
recording split now has gapless timing
scene monitor now guarantees min sample time
renamed a bunch of stats
added names to debug thread view on windows

improved calculation of display range for stat bars

added percentage/ratio units
added auto-range and auto tick calculation to stat bar to automate display stats

revert the changeset 54cf2fe4820a for SH-4264 to fix SH-4315: Interesting: Viewer crash on login on Mac in LLViewerRegion::updateVisibleEntries(float) and
SH-4316: Interesting Viewer Crash/freeze on Login to Levy region on Aditi with cleared cache on Windows XP

stat definition as they don't work on gcc/clang

also, removed LLTrace::init and cleanup
removed derived class implementation of memory stat for LLMemTrackable
is automatic now

removed LLThreadLocalSingleton
collapsed all thread recorder classes to single type, LLTrace::ThreadRecorder
moved fasttimer stack head to llthreadlocalsingletonpointer via ThreadRecorder

added ability to force uniqueness of LLCopyOnWritePointer
converted more variables to units
added convenience function for unit constants