Indeed, I can reproduce your panic, using the current pkgsrc-archive from
ftp.netbsd.org dated 31-mar-2012.
The crash location is in pmap_activate() from m68k/m68k/pmap_motorola.c:
pmap_t pmap = l->l_proc->p_vmspace->vm_map.pmap;:
vm_map seems to be NULL.
As this function is common to all m68k ports, can you reproduce the crash on
other m68k machines (I have just Amiga hardware here)? Maybe it has
something to do with the last kmem changes.
The only non-Amiga m68k I have is a Mac running NetBSD 6, and it compiled m4 just fine. Hmmm...
John