language: Add not-swapped flag for signals

This is needed because GtkBuilder defaults to swapped when you specify
the object attribute.

tests/sample_errors/signal_exclusive_flags.blp

@@ -0,0 +1,5 @@
+using Gtk 4.0;
+
+$MyObject obj {
+  signal1 => $handler() swapped not-swapped;
+}

tests/sample_errors/signal_exclusive_flags.err

@@ -0,0 +1 @@
+4,33,11,'swapped' and 'not-swapped' flags cannot be used together

tests/sample_errors/signal_unnecessary_flags.blp

@@ -0,0 +1,6 @@
+using Gtk 4.0;
+
+$MyObject obj {
+  signal1 => $handler() not-swapped;
+  signal2 => $handler(obj) swapped;
+}

tests/sample_errors/signal_unnecessary_flags.err

@@ -0,0 +1,2 @@
+4,25,11,'not-swapped' is the default for handlers that do not specify an object
+5,28,7,'swapped' is the default for handlers that specify an object

tests/samples/signal_not_swapped.blp

@@ -0,0 +1,5 @@
+using Gtk 4.0;
+
+Button obj {
+  clicked => $handler(obj) not-swapped;
+}

tests/samples/signal_not_swapped.ui

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+DO NOT EDIT!
+This file was @generated by blueprint-compiler. Instead, edit the
+corresponding .blp file and regenerate this file with blueprint-compiler.
+-->
+<interface>
+  <requires lib="gtk" version="4.0"/>
+  <object class="GtkButton" id="obj">
+    <signal name="clicked" handler="handler" swapped="False" object="obj"/>
+  </object>
+</interface>

tests/test_samples.py

@@ -200,6 +200,7 @@ class TestSamples(unittest.TestCase):
                 "expr_closure_args",
                 "parseable",
                 "signal",
+                "signal_not_swapped",
                 "template",
                 "template_binding",
                 "template_binding_extern",