GXemul Code2

Comments and minor fixes.

Moving OpenBSD/sgi from unsupported.html to guestoes.html.

Turning xy+freeze into its own "real" register.

Use full range 0x00 to 0xff for RGB values when input is RG3B2.

Taking the FR bit of the MIPS status register into account to use 64-bit floating point registers rather than pairs of 32-bit registers (need for OpenBSD/sgi to work).

256 MB of RAM is needed in OpenBSD/sgi in order to self-compile GXemul. 128 MB is not enough.

Removing old unused code.

Also print debug messages for NULL and FLUSH registers.

Better memory bank stuff for SGI O2 (128 vs 256 MB RAM).

Fixing some 8242 key encodings (used by the SGI O2 mode).