Sync toplevel configure.ac with GCC

Sync toplevel configure.ac with GCC

	Sync with GCC
	2015-06-02  Jason Merrill  <jason@redhat.com>

	PR bootstrap/66319
	* configure.ac: Use -std=gnu++98.

	2015-05-28  Mike Frysinger  <vapier@gentoo.org>

	* configure.ac (--vtable-verify): Use AS_HELP_STRING for help.
	* configure: Regenerate.

	2015-05-11  Paulo Matos  <paulo@matos-sorge.com>

	* configure.ac: Fix typo.
	* configure: Regenerate.

	2015-05-03  Matthias Klose  <doko@ubuntu.com>

	* configure.ac: Match $host configured with triplets.
	* configure: Regenerate.

	2015-04-17  Jakub Jelinek  <jakub@redhat.com>

	PR bootstrap/62077
	* configure.ac (--enable-stage1-checking): Default to
	release,misc,gimple,rtlflag,tree,types if --disable-checking
	or --enable-checking is not specified and DEV-PHASE is not
	experimental.
	* configure: Regenerated.

	2015-03-27  Uros Bizjak  <ubizjak@gmail.com>

	Install back PR target/47230 fix (Revert the revert).

config/

	Sync with GCC
	* mh-alpha-linux: Restored.