using --with-system-expat working when the system expat does not have
salted hash support.

in the hash table internal to the pyexpat module's copy of the expat
library to avoid a denial of service due to hash collisions.
Patch by David Malcolm with some modifications by the expat project.

    http://hg.python.org/cpython/rev/48705250232c
    changeset:   75187:48705250232c
    branch:      2.7
    parent:      75184:9a1d902714ae
    user:        Antoine Pitrou <solipsis@pitrou.net>
    date:        Wed Feb 22 22:16:25 2012 +0100

    changeset:   75153:9b7c6dd19e25
    branch:      2.7
    parent:      75151:b1a02c17b327
    user:        Antoine Pitrou <solipsis@pitrou.net>
    date:        Tue Feb 21 22:02:04 2012 +0100
    files:       Lib/test/test_os.py

    changeset:   75165:780008020c40
    user:        Antoine Pitrou <solipsis@pitrou.net>
    date:        Wed Feb 22 03:33:56 2012 +0100
    summary:     Fix (presumably) test_hash under big-endian systems (PPC).

Patch by Francisco Martín Brugué

have gotten randomized.

Closes #8033.