Updating LMDB to v 0.9.11, switching to gitorious

The homebrew version of LMDB does not provide all the defines that the [current version](http://symas.com/mdb/doc/lmdb_8h.html) does.

The latest LMDB code is provided, separate from the rest of OpenLDAP, in a [Gitorius repo](https://gitorious.org/mdb/mdb/source/).

This PR uses the latest tagged release of MDB, v. 0.9.11.