GXemul Code2

Fixing offset.

Finally fixed the bug which caused scroll-up to not work when running the O2 PROM.

Implementing the O2 GBE graphical (mouse) cursor; both bitmap and crosshair modes work exactly like on the real machine now.

Changing from 64 to 128 MB ram for the O2; this matches what my real O2 has, and it is now detected correctly both by OSes and the PROM.

NetBSD colors (RG3B2 mode) are now probably more correct. Filling the 24-bit framebuffer with non-8-bit data should now be more correct too.

Refactoring the O2 "output" to always be 24-bit, separate from the emulated framebuffer tiles (which may be e.g. 8 bit).

Some more emulated O2 registers now return the same values as my real O2 does.

OpenBSD can now show graphical console messages.

More SGI O2 graphics work: TLBs.

Continuing on the SGI O2 graphics; when the nr of tiles or "partial pixels" is in mismatch with the screen resolution, the skewed result now looks the same as on my real physical O2.