Set ARCH in such a way that it works for cross-building.  This should
be a no-op on like-for-like builds.  However, this change has the potential
of messing things up, so I will roll one final beta.
Update to 4.0.0.b2.
Properly check the syntax of MD_SIZE so that we can accept the k/m/g
suffix and won't error out if it is not defined.

Submitted by:	crees
Fix the Postgres migration code.  I think some MySQL slipped in there.

Submitted by:	kuriyama