Show a texture preview in addition to the framebuffer preview

It's cool to see what it's using to draw.

It's also interesting to see how we double up textures when bufw < w.  I wonder if we do crazy things when bufw > w, which is not impossible.  Maybe decoding could be faster if we just skipped the rest of the stride, not sure... but I wonder how the PSP reacts, actually, it probably does what we do for u/v values between bufw/w and 1.

Of course, there will be garbage at the bottom of many textures (unless they align to a power of 2 in height), but there's no way to know the correct height so that's life.

Also includes some code shuffling in preparation to make the softgpu return a texture also (which it does not yet), and a fix for savestates not loading properly anymore.

-[Unknown]