GXemul Code2

Minor progress on the LUNA88K framebuffer.

Adding a comment about experimenting with OpenBSD/luna88k second stage bootloader.

Continuing on interrupt stuff for LUNA88K, including the serial controller...

Basic interrupt controller and timer interrupt for LUNA88K.

Minor documentation updates. 0.6.1 is most likely the next release.

Removing notes about "legacy modes" in the documentation, since it was too ugly and those modes are pretty much the main focus of end-users of GXemul still.

Removing reference to sourceforge mailing lists.

Minor update.

OpenBSD/luna88k 5.3 and newer use a different syscall exception number.

OpenBSD/luna88k 5.2 (an older version) now reaches userland :-) issuing syscalls, but not 6.2 yet :-( and since no interrupts are implemented yet, it doesn't really do much.