giomodule.c: Include Some Forgotten Headers

The headers are used for G_TYPE_INITABLE and
G_NETWORK_MONITOR_EXTENSION_POINT_NAME, which led to undefined variables
if not included...

gio/giomodule.c

@@ -35,6 +35,8 @@
 #include "gtlsbackend.h"
 #include "gvfs.h"
 #include "gnotificationbackend.h"
+#include "ginitable.h"
+#include "gnetworkmonitor.h"
 #ifdef G_OS_WIN32
 #include "gregistrysettingsbackend.h"
 #endif