PR ada/6637, PR ada/5911
	Merge with libada-branch:
	* configure.in, Makefile.tpl, Makefile.def: Add target-libada,
	with appropriate dependencies. Add --enable-libada configure switch.
	* configure, Makefile.in: Regenerate.

Co-Authored-By: Nathanael Nerode <neroden@gcc.gnu.org>

From-SVN: r77594