Add "window-created" signal to MetaDisplay, "unmanaged" signal for MetaWindow

For some consumers it's significantly more convenient to be able
to directly connect to a signal on the Window to know when
Mutter is done with it, rather than having to connect to each
Workspace object (and handle workspace additions, etc.).

Similarly, add window-created which acts globally.

https://bugzilla.gnome.org/show_bug.cgi?id=598289

src/core/window.c

@@ -146,6 +146,7 @@ enum
   WORKSPACE_CHANGED,
   FOCUS,
   RAISED,
+  UNMANAGED,
 
   LAST_SIGNAL
 };
@@ -322,6 +323,15 @@ meta_window_class_init (MetaWindowClass *klass)
                   NULL, NULL,
                   g_cclosure_marshal_VOID__VOID,
                   G_TYPE_NONE, 0);
+
+  window_signals[UNMANAGED] =
+    g_signal_new ("unmanaged",
+                  G_TYPE_FROM_CLASS (object_class),
+                  G_SIGNAL_RUN_LAST,
+                  G_STRUCT_OFFSET (MetaWindowClass, unmanaged),
+                  NULL, NULL,
+                  g_cclosure_marshal_VOID__VOID,
+                  G_TYPE_NONE, 0);
 }
 
 static void
@@ -1081,6 +1091,8 @@ meta_window_new_with_attrs (MetaDisplay       *display,
 
   window->constructing = FALSE;
 
+  meta_display_notify_window_created (display, window);
+
   return window;
 }
 
@@ -1453,6 +1465,8 @@ meta_window_unmanage (MetaWindow  *window,
 
   meta_error_trap_pop (window->display, FALSE);
 
+  g_signal_emit (window, window_signals[UNMANAGED], 0);
+
   g_object_unref (window);
 }