Enable autoload in editor

- Tool scripts will be executed and can be accessed by plugins.
- Other script languages can implement add/remove_named_global_constant
to make use of this functionality.

modules/gdscript/gdscript_compiler.h

@@ -94,6 +94,9 @@ class GDScriptCompiler {
 
 		HashMap<Variant, int, VariantHasher, VariantComparator> constant_map;
 		Map<StringName, int> name_map;
+#ifdef TOOLS_ENABLED
+		Vector<StringName> named_globals;
+#endif
 
 		int get_name_map_pos(const StringName &p_identifier) {
 			int ret;