Initial stab at tracking vertex alpha.

Not sure what efficient method to use on x86...
Switch to fullAlphaReg not hasAlphaReg.
Correctly keep track of "full alpha" in vertices (x86 jit only).
Merge branch 'vertexalpha' of github.com:unknownbrackets/ppsspp into unknownbrackets-vertexalpha
Merge branch 'unknownbrackets-vertexalpha' into avoid-alpha-test

Conflicts:
	GPU/GLES/VertexDecoderX86.cpp
Eliminate further alpha tests
ARM buildfix
More checks for alpha test elimination
Merge pull request #5710 from hrydgard/avoid-alpha-test

Avoid alpha test when vertexFullAlpha && textureFullAlpha
Win32/NVidia: switch to fullscreen after showing the window. Fixes a weird issue with vsync being ignored otherwise.
Disable the adaptive vsync checks by commenting them out. No need to have a disabled check run every frame.
Don't calculate lighting when not enabled.

We just ignore it anyway.  2% improvement in Tales of Phantasia X.
Add prefetch to xxhash func on gcc at least.

Improves hashing speed on Android by ~18%.
Add a NEON-optimized version of XXH32.

This takes at least 40% less time to hash on NEON/ARM devices.
Make it possible to load a savestate in headless.

This is primarily useful to reproduce crashes or test performance.
Attempt to load VFS in headless on Android.

Otherwise we don't get fonts, and savestates fail to load.
Merge pull request #5721 from unknownbrackets/headless

Allow headless to load savestates
Merge pull request #5719 from unknownbrackets/gpu-minor

Don't calculate lighting when not enabled (software transform)
Use defines on x86/SSE to avoid func pointers.

Unfortunately no such luck for Android.
Merge pull request #5720 from unknownbrackets/texcache

Optimize xxHash for ARM/NEON devices