libthr and 1:1 threading.

I have commited libthr.  To try this out you'll need to do the following

1.  cvsup
2.  rebuild world and kernel
3.  install world and kernel
4.  build libthr from src/lib/libthr
5.  Either replace /usr/lib/libc_r.so.5 with /usr/lib/libthr.so.1 or
relink your applications against libthr.so.1

This works with mozilla and open office.

Known errata:
1.  Mutex priority inheritance is not implemented.
2.  If you mess with the mutex or condvar queues from a signal handler you
will break.
3.  If you reset the sigaction for SIGTHR you will break things.
4.  The scheduling parameters lie.
5.  The garbage collector deadlocks.  We never free threads.  You will
eventually leak memory or run out of LDT entries.
6.  This is x86 only for a short while.
7.  Some of the code is ugly.

I will be addressing all of this shortly.  Feel free to try it out and
report bugs that are not mentioned above.

Cheers,
Jeff