Include Couchstore 2.5.1 changes in rel-2.5.1

Changes included:

 * http://review.couchbase.org/#/c/33948/

Change-Id: I5389c95e22321324b551108fa5cf448ca0a555b0
Reviewed-on: http://review.couchbase.org/34113
Reviewed-by: Philip Labee <philip@couchbase.com>
Tested-by: Philip Labee <philip@couchbase.com>