Use find_opt instead of linear search through options in
handle_pragma_diagnostic (PR 49654) and reject non-warning options and
options not valid for the current language (PR 49655).

gcc/testsuite/ChangeLog:

2015-09-23  Manuel López-Ibáñez  <manu@gcc.gnu.org>

	PR c/49655
	* gcc.dg/pragma-diag-6.c: New test.

gcc/ChangeLog:

2015-09-23  Manuel López-Ibáñez  <manu@gcc.gnu.org>

	PR c/49655
	* opts.h (write_langs): Declare.
	* opts-global.c (write_langs): Make it extern.

gcc/c-family/ChangeLog:

2015-09-23  Manuel López-Ibáñez  <manu@gcc.gnu.org>

	PR c/49654
	PR c/49655
	* c-pragma.c (handle_pragma_diagnostic): Detect non-warning
	options and options not valid for the current language.

From-SVN: r228049