configure.in patch for hpux 10.20 DCE thread build

[Jeffrey A Law]

  In message <200006051650.MAA18072@hiauly1.hia.nrc.ca>you write:
  > Hi Jeff,
  > 
  > I sent this patch in quite a while ago, so I thought I would draw it
  > to your attention again.  It corrects a long standing problem with
  > building and linking with gcc when DCE threads are installed.  I hope
  > you will review and install it.  I use it in all my builds and it
  > has been thoroughly tested, both with and without -threads.
Not lost.  Just way back in the queue :-)

  > 2000-06-05  J. David Anglin  <dave@hiauly1.hia.nrc.ca>
  > 
  > 	* configure.in: Use default thread_file even when enable_threads is
  > 	yes or dce because hpux10.20 pa port uses MULTILIB implementation.
Thanks.  Installed.
jeff