SSA backend update

[Stephen Weeks]

> OK, I'll compile using an NJ-G0 and start playing with gdb ...

Well, no luck yet.  Matthew, I've put my latest snapshot at 

	http://www.star-lab.com/sweeks/src.tgz

if you're interested to take a look.  Right now, I'm trying to understand why
regression test 16 works fine if you run it without redirection, but fails when
rredirecting to a file.  The failure mode is to output nothing and exit with
status 0.  As best as I can tell with gdb, flush is confused and never calls
Posix_IO_write.  I'll look into it on Monday.