gdb: update gnulib to pull in C++ namespace support fixes

gdb: update gnulib to pull in C++ namespace support fixes

I've been experimenting with making use of gnulib's C++ namespace support:

 https://www.gnu.org/software/gnulib/manual/html_node/A-C_002b_002b-namespace-for-gnulib.html

That stumbled on a few gnulib issues, which I've fixed upstream:

 [PATCH] Fix gnulib C++ namespace support and std::frexp
 https://lists.gnu.org/archive/html/bug-gnulib/2016-11/msg00039.html

 [PATCH] Fix real-floating argument functions in C++ mode
 https://lists.gnu.org/archive/html/bug-gnulib/2016-11/msg00049.html

 [PATCH] Avoid having GNULIB_NAMESPACE::func always inject references to rpl_func
 https://lists.gnu.org/archive/html/bug-gnulib/2016-11/msg00040.html

 [PATCH] C++: "#define timeval rpl_timeval" -> typedef in GNULIB_NAMESPACE
 https://lists.gnu.org/archive/html/bug-gnulib/2016-11/msg00058.html

This merge pulls those in.

gdb/ChangeLog:
2016-11-15  Pedro Alves  <palves@redhat.com>

	* gnulib/update-gnulib.sh (GNULIB_COMMIT_SHA1): Set to
	38237baf99386101934cd93278023aa4ae523ec0.
	* gnulib/configure, gnulib/config.in: Regenerate.
	* gnulib/import/Makefile.am: Regenerate.
	* gnulib/import/Makefile.in: Regenerate.
	* gnulib/import/canonicalize-lgpl.c: Update.
	* gnulib/import/extra/snippet/c++defs.h: Update.
	* gnulib/import/m4/stdint.m4: Update.
	* gnulib/import/m4/stdlib_h.m4: Update.
	* gnulib/import/math.in.h: Update.
	* gnulib/import/stdlib.in.h: Update.
	* gnulib/import/sys_time.in.h: Update.