fix for libf2c installation

[Jeffrey A Law]

  In message < rzq67hv62c1.fsf@djlvig.dl.ac.uk >you write:
  > This seems to be the right way to fix the problem of libsubdir not
  > being defined for libf2c installation.
Agreed.  It's basically what I outlined to Craig recently.

  > [I don't understand why INSTALL is set explcitly to the shell script
  > rather than configured and why @AR@ and @RANLIB@ aren't used; their
  > definitions in configure could be removed as it is.]
Good questions.  No clue.  Probably be a simple oversight or historical
baggage that we haven't killed.

jeff