bsddb185 module changes checked in

[Skip Montanaro]

The various bits necessary to implement the "build bsddb185 when
appropriate" have been checked in.  I'm pretty sure I don't have the best
possible test for the existence of a db library, but it will have to do for
now.  I suspect others can clean it up later during the beta cycle.  The
current detection code in setup.py should work for Nick on OSF/1 and for
platforms which don't require a separate db library.

I'd appreciate some extra pounding on this code.

Thanks,

Skip