glsl: Allow 'in' and 'out' when 'layout' is also available

All of the extensions that add the 'layout' keyword also enable (and
required) the use of 'in' and 'out' with shader globals.

This is related to (piglit) bugzilla #31804.

NOTE: This is a candidate for the 7.9 and 7.10 branches.

src/glsl/ast_to_hir.cpp

@@ -2088,9 +2088,12 @@ ast_declarator_list::hir(exec_list *instructions,
        *
        *     Local variables can only use the qualifier const."
        *
-       * This is relaxed in GLSL 1.30.
+       * This is relaxed in GLSL 1.30.  It is also relaxed by any extension
+       * that adds the 'layout' keyword.
        */
-      if (state->language_version < 130) {
+      if ((state->language_version < 130)
+	  && !state->ARB_explicit_attrib_location_enable
+	  && !state->ARB_fragment_coord_conventions_enable) {
 	 if (this->type->qualifier.flags.q.out) {
 	    _mesa_glsl_error(& loc, state,
 			     "`out' qualifier in declaration of `%s' "