[geos-devel] GeomUnion shortcircuit tests

[strk at refractions.net]

As suggested by Bill I've implemented short circuit tests
in GEOS' Union operation: when bounding boxes of input geoms
are disjoint we just merge the two geoms in a collection, avoiding
to build graphs, node, etc...

HEAD & 2-1 branches updated.

Bill, if you have GEOS source code you can uncomment a debugging
line inside the short-circuit test so to be warned when the
disjoint-bboxes happen. This could help checking how number 
of occurrences relate to different types of sorting.

--strk;