libstdc++: Install GDB pretty printers for debug library

libstdc++: Install GDB pretty printers for debug library

The additional libraries installed by --enable-libstdcxx-debug are built
without optimization to aid debugging, but the Python pretty printers
are not installed alongside them. This means that you can step through
the unoptimized library code, but at the expense of pretty printing the
library types.

This remedies the situation by installing another copy of the GDB hooks
alongside the debug version of libstdc++.so.

Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:

	* python/Makefile.am [GLIBCXX_BUILD_DEBUG] (install-data-local):
	Install another copy of the GDB hook.
	* python/Makefile.in: Regenerate.

(cherry picked from commit db853ff78a34fef25bc16133e0367a64526f9f4e)