* 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
