Add back second texcache, improve perf, add memory check

This does a few things, all related to the texture cache:

 * Adds back the secondary texture cache.  For perf, it's only checked based on # of invalidations.  For games that draw animation over a texture, this should improve perf at the cost of VRAM.

 * Uses SSE2 in QuickTexHash.  This improves its performance significantly (I couldn't get MSVC to do this for me automatically, tried a couple variations...)  In Popolocrois (where this function was dominating at ~25%), it went from 500 to 600 vps with this change.

 * Checks for GL_OUT_OF_MEMORY, and starts decimating more and kills the second cache if it happens.  I was able to (at least on desktop) trigger this error, and this could even improve performance on some systems (but there's no way to tell when it's swapping into RAM afaict...)

-[Unknown]