There's a chunk of memory in LSI pmon that is supposed to contain
pointers to `system call' handlers.  However, sim_open() will
clobber the valid addresses it stores in this table with code bare
code (as opposed to pointers to code) that was meant to catch invalid
accesses.  This is obviously wrong.  I'm checking this in, since Frank
Ch. Eigler and Eric Christopher agreed it was a reasonable thing to
do.  I'll leave the complete fix for someone who has a real
understanding of what was supposed to be done there.