GXemul Code2

Adding a patch from Luchezar Georgiev for missing variant of ot for 88100 (immediate argument), and for missing addu_cio and subu_cio instructions.

Copyright year update.

Include ASID and VPN2 in MIPS load/store misalignment exceptions (patch from Nick Hudson).

Add comment about checking R10000 specifics.

Adding stdio.h include, required for build with some gcc versions on Linux. Noticed by Michael Mikonos.

Minihack to allow reading the bootloader from IRIX formatted disk, NetBSD install CDROM, and OpenBSD install CDROM.

SGI boot / partition work-in-progress.

Some minor refactoring of arcbios environment variables etc, to attempt to get emulated O2 boot-from-disk image (or cdrom image) to work better.

The ECOFF file loader can now (barely) load relocated binaries, such as "sash" from an IRIX installation on my real O2.

One -v on the command line should be enough to see file loading details.