patch to autoconfiscate vfork handling

[Jeffrey A Law]

  In message <199810301531.KAA17171@caip.rutgers.edu>you write:
  > 	This patch adds autoconf support for vfork instead of checking
  > macro USG.  I included changes to the gcc dir (for collect2.c) as well
  > as a libiberty dir change (for pexecute.c) in this one file since they
  > go together and were relatively small.
  > 
  > 
  > 	The libiberty/pexecute.c changes didn't require using
  > AC_FUNC_VFORK since libiberty/configure.in already calls it. 
  > 
  > 	Okay to install?
They look fine to me.


At first I thought we had potential canadian cross problems, but then I 
remembered that pexecute.c is built for the host, not the build machine
within the gcc dir itself.


jeff