Thread config diffs for 971215.

[Jeffrey A Law]

  In message < 199712181312.OAA18778@lev.labs.trema.com >you write:
  > Here are diffs to make thread handling more configurable.  It also
  > includes a fix to one problem which it is hard to isolate because I
  > have split libgcc-thr.h to multiple files.
  > 
  > With these changes, thread support is enabled by default on
  > sparc/solaris2, using weak symbols, so multilib definitions are gone.
  > configure prefers pthreads over solaris threads, but the default can
  > be changed with --enable-threads=solaris.
  > 
  > In pa/hpux10, thread support is enabled by default if pthread.h is
  > found, and is implemented using multilibs.
  > 
  > Since --enable-threads affects also objc, objc/thr-dce.c is a copy of
  > objc/thr-decosf1.c.  Maybe we should get rid of the latter one since
  > it seems to be DCE threads.
[ ... ]
Thanks!  I've installed these patches.

jeff