Log Message:
Updated mdds1.2 to 1.2.3.

mdds 1.2.3

* all

  * changed the configure script to use --docdir unmodified.

* flat_segment_tree

  * added a segment iterator whose node value consists of the start
    and end keys and the value associated with each segment.  its
    start and end positions can be retrieved via begin_segment() and
    end_segment() methods.