Add missing public statics to NotificationCompat

To match the ones currently on Notification, with the
exception of EXTRA_SHOW_WHEN since setShowWhen is not in
NotificationCompat yet (will file bug for setShowWhen since it
was an API 17 addition)

Change-Id: Iedbf2455d4be093a3d6fbc9b9d237d0f6cc1fd67
1 file changed