Fix missing gthr-default.h issue on separate libstdc++ configure

    Fix missing gthr-default.h issue on separate libstdc++ configure
        * acinclude.m4: Define glibcxx_thread_h.
        * include/Makefile.am: Use glibcxx_thread_h.
        * Makefile.in: Regenerate.
        * configure: Regenerate.
        * doc/Makefile.in: Regenerate.
        * include/Makefile.in: Regenerate.
        * libsupc++/Makefile.in: Regenerate.
        * po/Makefile.in: Regenerate.
        * python/Makefile.in: Regenerate.
        * src/Makefile.in: Regenerate.
        * src/c++11/Makefile.in: Regenerate.
        * src/c++98/Makefile.in: Regenerate.
        * testsuite/Makefile.in: Regenerate.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/gcc-4_7-branch@192309 138bc75d-0d04-0410-961f-82ee72b054a4