datastore.h

[Gyepi SAM]

Hi,

I just realized that datastore.h has now been split
up into datastore.h and datastore_db.h, but everything in
datastore_db.h should be in datastore.h since datastore.h presents
the API for implementing a database independent datastore.

While we happen to be using BDB now, there's no reason why we could not switch or
offer alternatives in the future. In fact, I am now investigating tdb (http://tdb.sf.net),
which was recommended by a list member. Thanks Yusuf!

Unless there's some compelling reason not to, I'd like to combine the
two files...

-Gyepi