[binutils-gdb] Add --with-system-zlib to top level configure

[sergiodj+buildbot@redhat.com]

*** TEST RESULTS FOR COMMIT cf39cfc52ebd683d55fc396a77355f34b5094c04 ***

Author: H.J. Lu <hjl.tools@gmail.com>
Branch: master
Commit: cf39cfc52ebd683d55fc396a77355f34b5094c04

Add --with-system-zlib to top level configure
The top level configure supports --with-system-zlib.  This patch makes
configure --help to display --with-system-zlib.

	* configure.ac: Add --with-system-zlib.
	* configure: Regenerated.