merge ktrace-lwp.

move spl*() and IPL_* definitions from psl.h to intr.h.

de-__P, remove register, ansify, b* -> mem*, u_int*_t -> uint*_t.

Now define splzs() here.

Added sources for the sun2 boot blocks and other
sun68k-ish code, all of which ought to eventually
be shared with the sun3.