top-level conigure.in patch

[David Edelsohn]

	I have write access to the gdb CVS tree.  Do you want me to commit
the patches directly when they are accepted on the gcc tree?

	The reason that I want to ensure that -fPIC is not included in the
compiler options is that all AIX PowerPC code is PIC and -fpic/-fPIC is an
error.  I also have re-worked the libiberty, libio, and libstdc++
Makefiles so that creating pic versions of object files depends on
$(PICFLAGS), not $(enable_shared), so this ensure that PICFLAGS is defined
properly to coordinate with that change.  These changes allow the proper
creation of AIX shared libraries.

David