glsl: Add missing location info to case labels.

Otherwise, the upcoming error messages said the location was 0:0(0).

NOTE: This is a candidate for the 8.0 branch.

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>

src/glsl/glsl_parser.yy

@@ -1691,10 +1691,12 @@ case_label:
 	CASE expression ':'
 	{
 	   $$ = new(state) ast_case_label($2);
+	   $$->set_location(yylloc);
 	}
 	| DEFAULT ':'
 	{
 	   $$ = new(state) ast_case_label(NULL);
+	   $$->set_location(yylloc);
 	}
 	;