Bind vararg method flag in core constants

(cherry picked from commit 1f361b03678893cd6328702383fce6dc062e7e57)

core/global_constants.cpp

@@ -634,6 +634,7 @@ void register_global_constants() {
 	BIND_GLOBAL_ENUM_CONSTANT(METHOD_FLAG_REVERSE);
 	BIND_GLOBAL_ENUM_CONSTANT(METHOD_FLAG_VIRTUAL);
 	BIND_GLOBAL_ENUM_CONSTANT(METHOD_FLAG_FROM_SCRIPT);
+	BIND_GLOBAL_ENUM_CONSTANT(METHOD_FLAG_VARARG);
 	BIND_GLOBAL_ENUM_CONSTANT(METHOD_FLAGS_DEFAULT);
 
 	BIND_GLOBAL_ENUM_CONSTANT_CUSTOM("TYPE_NIL", Variant::NIL);

doc/classes/@GlobalScope.xml

@@ -1545,6 +1545,8 @@
 		<constant name="METHOD_FLAG_FROM_SCRIPT" value="64" enum="MethodFlags">
 			Deprecated method flag, unused.
 		</constant>
+		<constant name="METHOD_FLAG_VARARG" value="128" enum="MethodFlags">
+		</constant>
 		<constant name="METHOD_FLAGS_DEFAULT" value="1" enum="MethodFlags">
 			Default method flags.
 		</constant>