Allow system images larger than 2GiB.

Python 2.7's zipfile implementation wrongly thinks that zip64 is
required for files larger than 2GiB. We can work around this by
adjusting their limit. Note that `zipfile.writestr()` will not work
for strings larger than 2GiB. The Python interpreter sometimes rejects
strings that large (though it isn't clear to me exactly what
circumstances cause this). `zipfile.write()` must be used directly to
work around this

This mess can be avoided if we port to python3.

The bug (b/19364241) in original commit has been fixed.

Bug: 18015246
Bug: 19364241
Bug: 19839468

(cherry picked from commit cd082d4b)

Change-Id: I7b5cc310e0a9ba894533b53cb998afd5ce96d8c6