This patch adds generic support for the Ada.Locales package that
relies on the setlocale() C service.

2018-05-22  Javier Miranda  <miranda@adacore.com>

gcc/ada/

	* locales.c: New implementation for the Ada.Locales package.
	* libgnat/a-locale.ads: Remove comment indicating that this is not
	implemented.
	* doc/gnat_rm/standard_library_routines.rst: Remove comment indicating
	that this is not implemented.
	* gnat_rm.texi: Regenerate.

From-SVN: r260509