Makefile.in (site.exp): Define HAVE_LIBSTDCXX_V3.

Makefile.in (site.exp): Define HAVE_LIBSTDCXX_V3.

	* Makefile.in (site.exp): Define HAVE_LIBSTDCXX_V3.
	* configure.in (enable-libstdcxx-v3): Arrange to have
	HAVE_LIBSTDCXX_V3 substituted into the output files.

	* lib/g++.exp (g++_include_flags): Trust HAVE_LIBSTDCXX_V3
	to tell us whether or not we are using V3.

	* Makefile.in (check): Don't make mkcheck executable.
	(check-install): Likewise.
	* configure.in (AC_OUTPUT): Make mkcheck executable.
	* mkcheck.in (top_srcdir): New variable.
	(INC_PATH): Set the path to the backward and ext directories
	correctly.

From-SVN: r37068