Hi folks,

In an effort to get the m68k-based ports sharing more kernel code, I'm
about to move syscall() and child_return() into m68k/syscall.c. Right now,
each port has its own ~identical version of syscall(). The only
differences are mild bit-rot, and slight variations to userret(). My
changes address both those.

One of the main benefits of this is that it reduces the amount of work
required to make each port work with ELF binaries.

There is still a bunch more code which could be unified, eg. trap(), and
with a bit of luck I will address that next year.

Comments before I commit? Of course, I can only test this on mvme68k, so
I may inadvertently cause a few problems which should be easy to resolve.

Cheers, Steve