Import gnulib's mkdir module

The following patch makes use of the mkdir function.  Import the mkdir
gnulib module to ensure proper operation on all platforms.

gdb/ChangeLog:

	* gnulib/aclocal.m4: Re-generate.
	* gnulib/config.in: Re-generate.
	* gnulib/configure: Re-generate.
	* gnulib/import/Makefile.am: Re-generate.
	* gnulib/import/Makefile.in: Re-generate.
	* gnulib/import/m4/gnulib-cache.m4: Re-generate.
	* gnulib/import/m4/gnulib-comp.m4: Re-generate.
	* gnulib/import/m4/mkdir.m4: New file.
	* gnulib/import/mkdir.c: New file.
	* gnulib/update-gnulib.sh (IMPORTED_GNULIB_MODULES): Add mkdir
	module.