Initial implementation of the message tray and notification daemon

From the message-tray branch. Most of the UI parts were written by
Marina, and most of the D-Bus parts by me.

src/gnome-shell.in

@@ -357,8 +357,9 @@ try:
     shell = None
     if options.xephyr:
         xephyr = start_xephyr()
-        # This makes us not grab the org.gnome.Panel name
-        os.environ['GNOME_SHELL_NO_REPLACE_PANEL'] = '1'
+        # This makes us not grab the org.gnome.Panel or
+        # org.freedesktop.Notifications D-Bus names
+        os.environ['GNOME_SHELL_NO_REPLACE'] = '1'
         shell = start_shell()
     else:
         xephyr = None

src/shell-global.c

@@ -751,7 +751,7 @@ shell_global_grab_dbus_service (ShellGlobal *global)
    * unless a special environment variable is passed.  The environment
    * variable is used by the gnome-shell (no --replace) launcher in
    * Xephyr */
-  if (!g_getenv ("GNOME_SHELL_NO_REPLACE_PANEL"))
+  if (!g_getenv ("GNOME_SHELL_NO_REPLACE"))
     {
       if (!dbus_g_proxy_call (bus, "RequestName", &error, G_TYPE_STRING,
                               "org.gnome.Panel", G_TYPE_UINT,