The size fields in the data descriptor can be either 4 bytes or 8 bytes.
This depends on if the size are read from the zip64 extended field in
the local file header. This cl adds support to parse these cases.
Also fix a misconception in that the uncompressed and compressed size
doesn't need to exist together in the zip64 fields of the central
directory. But they still need to co-exist in the fields of the local
file header.
Bug: 150900468
Test: unit tests pass, python tests pass
Change-Id: Ia54f9bf56c85ff456ead90a136f7fddc5be5220c
0ec0eaa214