eliom.3.0.3: add Grégoire's int64 patch


This patch is also in Eliom's Darcs repo ([there](http://ocsigen.org/darcsweb/?r=eliom.dev;a=commit;h=20130103165922-66bed-be0c05589835aee0ce4b9b3179f66056d25e095c.gz)), and will be in 3.0.4, but the bug was *blocking* for us, so maybe it is useful for someone else.