configure forces use of threads under 10.20

[Jeffrey A Law]

  In message < 199910291630.MAA18044@hiauly1.hia.nrc.ca >you write:
  > Under HP-UX 10.20, if configure finds pthread.h, it enables threads.
  > It is not possible to disable threads in this situation.  The logic
  > of the test is wrong.  What should be done is to disable threads if
  > pthread.h is not found, and to require the user to explicitly enable
  > threads (i.e., default is disabled).  I have included a small patch
  > to correct this behaviour under gcc-2.95.2.
Actually, I think that what GCC is doing is the desired behavior.  What
makes you think that we should only enable thread support if the user
has asked for it?


  > Further work on configure is needed if the user wants to use the GNU
  > pth/pthread implementation in place of the HP DCE implimentation.  I
  > also believe that there are linking problems (i.e., specs needs to be
  > fixed) if --enable-shared and --enable-threads are both specified.
  > I haven't attempted to sort this out.
Yes, this stuff needs to be sorted out.  
jeff