Change all doc refs MDB->LMDB.
Drop reference to OpenLDAP.
Tweak installation notes.
Annotate error exits with unlikely().
Revert "Annotate error exits with unlikely()."

This reverts commit 20bb3c9892b702fc515f6dd25d764e296aa5f4e8.

It had no reliably measurable performance improvment, at least on an i7
960 and within a microbenchmark. Will reconsider this approach when a
larger test exists (i.e. one that saturates cache)
Document argument types.
Centralize iterator construction.

In preparation for adding freelist.
Add docs tracking
LMDB 0144da6eab00cf5f321d5c6794175485ba3efefd

Fix crash caused by iterating existing cursor following a delete.

Author: Howard Chu <hyc@symas.com>
Date:   Sat Sep 21 14:37:11 2013 -0700

    ITS#7701 fix mdb_rebalance

    Must copy tmp cursor back to real cursor when merging into tmp cursor.
LMDB 912e09fd04e0512e6f764176a4a0a2ab009c87d1

Author: Howard Chu <hyc@symas.com>
Date:   Sun Sep 15 13:08:29 2013 -0700

    ITS#7681 fix 18a07eb7c2dc33372455a6040984cd6b699b41a5

    Set rc=0 when taking the SET_RANGE branch
Bump version for release.