Pull changes to export gregset() functions up from the thread branch
since the port includes them always.  These are only needed for user
threads in fbsd-threads.c (i.e. for KSE or libc_r, not for anything
modern).
Remove the bsd-uthread callbacks.  This is a pull up from the threads branch
to match the port which always does this.
Merge branch 'freebsd-7.8' into freebsd-7.8-threads