GXemul Code2

Remove old link.

Patch from Luchezar Georgiev (unused variables when building without X11).

errno.h needed to build on OpenBSD/sgi inside the emulator.

Updating comment about years being 72 or 73 on DECstations.

Only add input from the lk201 keyboard (or serial port) when there is actual space available in the rx buffer. (Similarly to how the luna88k serial port is handled.)

Doc updates.

Handle return values from interrupted select() when checking for available console input. (Found when using CTRL-C on Linux to enter the debugger command line, and noticed that it was spuriously broken.)

Updating OpenBSD/sgi install instructions (6.5 -> 6.8), and including a screenshot of X11 running.

Removing RAMDISK example output from the docs.

Implementing mouse emulation support for the LUNA88K machine.