Stop using gtk_main and gtk_main_quit

Replace these calls with direct use of GMainContext api.

tests/testentrycompletion.c

@@ -286,6 +286,17 @@ match_selected_cb (GtkEntryCompletion *completion,
   return TRUE;
 }
 
+static void
+quit_cb (GtkWidget *widget,
+         gpointer   data)
+{
+  gboolean *done = data;
+
+  *done = TRUE;
+
+  g_main_context_wakeup (NULL);
+}
+
 int 
 main (int argc, char *argv[])
 {
@@ -295,11 +306,12 @@ main (int argc, char *argv[])
   GtkEntryCompletion *completion;
   GtkTreeModel *completion_model;
   GtkCellRenderer *cell;
+  gboolean done = FALSE;
 
   gtk_init ();
 
   window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
-  g_signal_connect (window, "destroy", gtk_main_quit, NULL);
+  g_signal_connect (window, "destroy", G_CALLBACK (quit_cb), &done);
   
   vbox = gtk_box_new (GTK_ORIENTATION_VERTICAL, 2);
   gtk_container_add (GTK_CONTAINER (window), vbox);
@@ -407,7 +419,8 @@ main (int argc, char *argv[])
 
   gtk_widget_show (window);
 
-  gtk_main ();
+  while (!done)
+    g_main_context_iteration (NULL, TRUE);
 
   return 0;
 }