Reduce size of ArrayData by one pointer

The pointer to the real data is not required anymore, as
it always follows the class itself. Like this we save one
pointer of overhead, and one indirection when doing reads
and writes of array data.

Change-Id: If6afdac8e97b57420b50e7b7eb8979f77e8dbbcf
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>