This commit eliminates all of the 'border' class and list code and replaces
it with testing if in the current region.
Impacts: can make a mega-region out of varregions of the same size; and
mega-region combinations must be rectangular (not square but rectangular)
An adaptation of part of Garmin's patch from http://opensimulator.org/mantis/view.php?id=5975, thanks!
Flag only written if the SW corner OAR is saved - this is the only one that captures object data presently (though not land or terrain data).
This adds an IRegionCombinerModule interface and the necessary methods on RegionCombinerModule
