r26244: Add a module (sans tests for the moment) that implements ranged

r26244: Add a module (sans tests for the moment) that implements ranged

results, as used particularly by MMC's Active Directory Users and
Computers to list group members.

This may be used on any attribute, but is useful to obtain attributes
that may be lengthy in 'pages'.  The implementation presumes that
attributes will always be returned by the DB in the same order.

Andrew Bartlett
(This used to be commit c789a91e00b47b2f02513e97101b9606d00c6aaa)