JIT64: clean up and unify float load/store code

While we're at it, support a bunch of float load/store variants that weren't
implemented in the JIT. Might not have a big speed impact on typical games but
they're used at least a bit in povray and luabench.

694 -> 644 seconds on povray.
DiscIO: Move VolumeDirectory off of raw pointers
Merge pull request #875 from lioncash/statics

DiscIO: Make the unordered set in IsSoundFile static
JIT64: add mulhwx implementation
PPCFP: add comment
Merge pull request #884 from FioraAeterna/ppcfpopt

PPCFP: add comment
Refactor SetCpStatus into two functions for from-GPU and from-CPU mode rather than a boolean parameter.

This shouldn't affect functionality.  I'm not sure if the breakpoint
distinction is actually necessary (my commit messages from the old
dc-netplay last year claim that breakpoints are broken anyway, but I
don't remember why), but I don't actually need to change this part of
the code (yet), so I'll stick with the trimmings change for now.
A tiny restructuring to allow inlining of FifoCommandRunnable.  Probably useless.
Add Flag support to ChunkFile.h
Unify three types of non-FIFO requests to the GPU thread around Common::Event and Common::Flag.

The only possible functionality change is that s_efbAccessRequested and
s_swapRequested are no longer reset at init and shutdown of the OGL
backend (only; this is the only interaction any files other than
MainBase.cpp have with them).  I am fairly certain this was entirely
vestigial.

Possible performance implications: efbAccessReady now uses an Event
rather than spinning, which might be slightly slower, but considering
the slow loop the flags are being checked in from the GPU thread, I
doubt it's noticeable.

Also, this uses sequentially consistent rather than release/acquire
memory order, which might be slightly slower, especially on ARM...
something to improve in Event/Flag, really.
JIT: Initial FPRF support

Doesn't support all the FPSCR flags, just the FPRF ones.
Add PPCAnalyzer support to remove unnecessary FPRF calculations.

POV-ray benchmark with enableFPRF forced on for an extreme comparison:
Before: 1500s
After, fmul/fmadd only: 728s
After, all float: 753s

In real games that use FPRF, like F-Zero GX, FPRF previously cost a few percent
of total runtime.

Since FPRF is so much faster now, if enableFPRF is set, just do it for every
float instruction, not just fmul/fmadd like before. I don't know if this will
fix any games, but there's little good reason not to.
Merge pull request #867 from comex/gpu-determinism-pr1

Some small preparatory changes to VideoCommon for GPU thread determinism mode.
Change default netplay buffer to 5.
Bugfixes for fmul rounding

Fix the places I forgot to add Force25Bit, and fix an incredibly silly typo bug
Merge pull request #887 from FioraAeterna/fmulinterp

Bugfixes for fmul rounding
Fix another absent-minded typo in the fmul interpreter patch
Merge pull request #888 from FioraAeterna/fmulinterp

Fix another absent-minded typo in the fmul interpreter patch
glx: fix shutdown hang
x64Emitter: add support for some missing CVT instructions
Re-enable the vertex loader JIT on OS X.

Why was it ever disabled?