pthread additions

[fortinj@ibm.net]

Hi all,

	I've implemented pthread_join, pthread_detach and pthread_exit to the 
existing thread functions.  I ran these through some basic testing for
function and they seem to work properly.  I did see some oddities using
printf and fprintf ( maybe problems in libc.a thread-safety ?)

	I also noticed that gdb does not seem to work with threads.  This could
be my fault as I am more used to dbx on aix.

The attached tar file includes diffs for: 
pthread.h 
pthread.cc
thread.cc 
thread.h
cygwin.din

These diffs are against the 3/28 snapshot.

As always, any and all comments are appreciated.

John Fortin,
fortinj@ibm.net
pthread.tar