regions testing

[Eric Dean Tribble <tribble>]

I finally came up with a decent way to test regions.  Rather than
spewing out 400k of regression test file (!), I simply do boolean
consistency checks.  such things as: 'b cannot intersect a minus b'.
This discovered several subtle bugs in PointRegions, but it also
detected some in IntegerRegion.  I expect we should use this style of
checking for all the region classes, and for sets as well.

dean