Highlight control flow keywords with a different color

This makes them easier to distinguish from other keywords.

modules/gdnative/pluginscript/pluginscript_language.h

@@ -71,6 +71,7 @@ public:
 
 	/* EDITOR FUNCTIONS */
 	virtual void get_reserved_words(List<String> *p_words) const;
+	virtual bool is_control_flow_keyword(String p_keyword) const;
 	virtual void get_comment_delimiters(List<String> *p_delimiters) const;
 	virtual void get_string_delimiters(List<String> *p_delimiters) const;
 	virtual Ref<Script> get_template(const String &p_class_name, const String &p_base_class_name) const;