hikaru/gpu: minor update to the annotations.
hikaru/renderer: fix typo ABGR4444 texhead decoding.
hikaru/gpu: remove calls to disasm from insns.
hikaru/renderer: improve texhead comparison.

When determining whether a texhead has already been decoded and cached, only
compare those bits that determine the location/format/size of the texture data.

Now enabling textures doesn't affect FPS at all.
hikaru/renderer: do not clear the texcache if not needed.
hikaru/{gpu,renderer}: annotate disable-culling bit.

And add a renderer option to debug face culling. Toggle with 'f'.
hikaru/renderer: remove unused macro.