Mutter 3.9.2 Supports String-Array Preferences

Mutter 3.9.2 adds the meta_window_can_close() function, adds support for string-array preferences, improves tracking of the focus window, adds an API to freeze/unfreeze the keyboard, and removes the overlay_group function. This development release of Mutter also fixes the shade window action and a potential race condition with _NET_WM_MOVERESIZE. Moreover, it now grabs and emits a signal when XK_ISO_Next_Group is pressed.