Fix build against latest glib

gir

@@ -1 +1 @@
-Subproject commit 89daf8f60096fb80b7a1eff67feb0bf1bf165ec4
+Subproject commit ac9a8dadb62d003af9f0c6ed46e82ff0971125e5

src/notification.rs

@@ -5,6 +5,8 @@ use glib::translate::*;
 use glib;
 use glib_ffi;
 use gobject_ffi;
+use std::mem;
+use std::ptr;
 use std;