Non-functional changes of numbers into symbolic references and a few
comments on what variables really mean.
Rewrite of mega-region code to use new form of border checking.
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)
Properly restore position on crossing failure for mega-regions.
Fix odd "cannot cross into banned parcel" viewer error message when crossing
into non-existant region. Proper permission failure messages are now returned.
Fix displacement and location operations on legacy trees and grass in
the 'load oar' and 'scene' commands. Before they  were ignored but the
code now relies on the SOG.IsAttachment function for attachmentness.