specialize region-* methods on (drei-area region) and vice versa (#548)
specialize region-* methods on (drei-area region) and vice versa (#548)


Previous specialization was (drei-area *).  We need this change to ensure
that our region-union, region-intersection, and region-difference methods,
which extract the bounding-rectangle of the drei area before re-calling the
region-* method, get called instead of methods that specialize on (region region).
slyrus/mcclim,slyrus/mcclim