Correctly exit from game when Alt+F4 pressed or 'x' button clicked.

See for details:
https://savannah.nongnu.org/bugs/?13163
https://savannah.nongnu.org/bugs/?17839
http://www.openbsd.org/cgi-bin/cvsweb/ports/games/crack-attack/patches/patch-src_gtk-gui_gui_main_cxx


--- crack-attack-1.1.14/src/gtk-gui/gui_main.cxx	2005-05-01 10:04:12 +0700
+++ crack-attack-1.1.15-cvs-01/src/gtk-gui/gui_main.cxx	2006-06-02 10:38:40 +0700
@@ -50,6 +50,18 @@
 int glut_argc;
 char **glut_argv;
 
+/* 
+ * Call this when the window is unexpectedly destroyed to make sure the
+ * hidden gui process doesn't hang around in the background.
+ */
+static void destroy_window(GtkObject *object, gpointer data) {
+#ifdef DEVELOPMENT
+	g_print("\nOh no! We've been unexpectedly destroyed! :(\n");
+#endif
+	gtk_main_quit();
+}
+
+
 /*
  * Documentation
  *   html tables don't work right in explorer
@@ -76,6 +88,8 @@
     winCrackAttackSplash = create_winCrackAttackSplash ();
 		gui_data_read(winCrackAttackSplash);
     gtk_widget_show (winCrackAttackSplash);
+		g_signal_connect(GTK_OBJECT(winCrackAttackSplash), "destroy",
+				G_CALLBACK(destroy_window), NULL);
     gtk_main ();
 
   return 0;