glsl/glcpp: Add a -d/--debug option to the standalone glcpp program

The verbose debug output from the parser is quite useful when debugging, and
having this available as a command-line option is much more convenient than
manually forcing this into the code when needed, (which is what I had been
doing for too long previously).

Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>

src/glsl/glcpp/glcpp.c

@@ -124,6 +124,7 @@ enum {
 const static struct option
 long_options[] = {
 	{"disable-line-continuations", no_argument, 0, DISABLE_LINE_CONTINUATIONS_OPT },
+        {"debug",                      no_argument, 0, 'd'},
 	{0,                            0,           0, 0 }
 };
 
@@ -140,11 +141,14 @@ main (int argc, char *argv[])
 
 	init_fake_gl_context (&gl_ctx);
 
-	while ((c = getopt_long(argc, argv, "", long_options, NULL)) != -1) {
+	while ((c = getopt_long(argc, argv, "d", long_options, NULL)) != -1) {
 		switch (c) {
 		case DISABLE_LINE_CONTINUATIONS_OPT:
 			gl_ctx.Const.DisableGLSLLineContinuations = true;
 			break;
+                case 'd':
+			glcpp_parser_debug = 1;
+			break;
 		default:
 			usage ();
 			exit (1);