Hide android.os.Parcel.obtain(int).

This will break on 64 bit because 64 bit pointers are
wider than java int.

Also, this method technically isn't a public API because
it's a protected method on a final class. It shows up in
our api.txt files because of a quirk in the API generation
system.

Change-Id: I2b574943008ed34696b048195c0cac6af1aa0a3b