Added system for GDScript warnings

- Count and panel per script.
- Ability to disable warnings per script using special comments.
- Ability to disable warnings globally using Project Settings.
- Option to treat enabled warnings as errors.

editor/plugins/script_text_editor.h

@@ -39,6 +39,7 @@ class ScriptTextEditor : public ScriptEditorBase {
 	GDCLASS(ScriptTextEditor, ScriptEditorBase);
 
 	CodeTextEditor *code_editor;
+	RichTextLabel *warnings_panel;
 
 	Ref<Script> script;
 
@@ -124,6 +125,8 @@ protected:
 	void _code_complete_script(const String &p_code, List<String> *r_options, bool &r_force);
 	void _load_theme_settings();
 	void _set_theme_for_script();
+	void _toggle_warning_pannel(const Ref<InputEvent> &p_event);
+	void _warning_clicked(Variant p_line);
 
 	void _notification(int p_what);
 	static void _bind_methods();