version compare and partial orgls

[Eric Dean Tribble <tribble>]

Mark and I just resolved the semantics of the version comparison
operations when applied to partial orgls.  The result was delightfully
trivial: their semantics don't change.  Since the comparison
operations compare the differences between the coordinate spaces, it
doesn't matter whether any data is associated with locations in the
coordinate space!  

As a result, only the unify operation can modify sharing relationships
(that's exactly what it's for).  Unify adds the information that two
initially unshared spaces now refer to the exact same thing.  Hmm.  My
quick 'semantics' for unify implies that two partial orgls can be
unified.  Bizarre.  It makes sense, though.

dean

PS  This reinforces our decision in the design of the semantics to
separate unify on berts and inform of partial orgls.  Semantically,
the operations are very similar, and wee were tempted to unify them.
Or is that inform them....