Optimize > and != 0 alpha tests.

There's no need to do rounding in this case.  These are very common.

Also, if the test was !=, convert it to >, which may work better on
PowerVR.
Optimize ComputeFragmentShaderID() a bit.

I've seen it decently high on some profiles (1-2%).  This cuts it down by
12.5% when used in a tight loop.  The temporary was 8%, the ifs were the
other 4.5%.
Optimize ComputeVertexShaderID() a bit.

This is only like 1%.  Along the way found and fixed an overlap of bits.
Merge pull request #5762 from unknownbrackets/gpu-minor

Shader ID optimizations and alpha test optimization
Cleanup SimpleAudioDec
and remove unused AudioCreate fonction, it can be down in the class constructor.
Update some flags in GLES_GPU.

It's useful to know if we need to have a correct PC value or downcount.
Merge pull request #5766 from unknownbrackets/gpu-minor

Update some flags in GLES_GPU
Fix performance issue in BlockCache due to an instance of std::vector in every block:

Avoid creating the vector when not necessary.

This was especially noticeable in debug mode.
Reduce some includes under GPU/.
Include sceKernelThread.h in less headers.
Fix sceUtilityScreenshotUpdate

Fix "After the developer/publisher screen and the age warning only a
black screen."
Avoid a crash with a huge user memory font size.

Fixes tests.
Add some basic bounds checking for power freq sets.
Fix sceUtilityScreenshotInitStart parameter
Imp sceUtilityScreenshotContStart
Skip flushing FPU/VFPU regs if none were allocated.

They're not used as often, so this usually saves time.  About 1% during
tests.
Cut time in EstimatePerVertexCost().

From profling, this cuts 4% time while lighting is enabled, and 14% while
disabled (on ARM.)  But maybe should just inline this...
Ensure stuff run on every prim are inlined.

These both get a ton of calls and show up on profiles.
Revent back status = SCE_UTILITY_STATUS_FINISHED

break Project Divx extand and Kenka Banchou Bros when take screenshot
Fix some memory leaks in sceFont.

Which were highlighted quite well by tests.