small libf2c cleanups

[Jeffrey A Law]

  In message < rzqlnzp3ov1.fsf@djlvig.dl.ac.uk >you write:
  >  Craig> Anyway, to teach g77 that an intrinsic returns a pointer as a
  >  Craig> function value, change gcc/f/com-rt.def so its entry starts
  >  Craig> with "Ip:", a la LOC.
  > 
  > ... but this change would be incompatible.
Sorry, but I don't follow all this...  Just not familiar enough with g77.

Any thoughts on backing out the signal_.c patch until y'all come up with
a suitable solution for the intrinsics?

jeff