Fix a major bug in Bundle when unparcelling from AIDL.

There was a serious problem in the Bundle(Parcel) and readFromParcel() methods,
where it wasn't doing the copying of the Parcel that Parcel.readBundle() does
and is a basic requirement for it to work correctly.

This re-arranges the code to make all of these functions (hopefully) correct.

Also fix a problem in Parcel where we were not duping fds when copying data from
one Parcel to another.