Add named colors to GDScript/Visual Script/core.

Names and values taken from https://en.wikipedia.org/wiki/X11_color_names

modules/visual_script/visual_script_builtin_funcs.h

@@ -66,6 +66,7 @@ public:
 		STR_TO_VAR,
 		VAR_TO_BYTES,
 		BYTES_TO_VAR,
+		COLORN,
 		FUNC_MAX
 	};