Backport of:

revno: 3363.3.16
revision-id: jorgen.loland@oracle.com-20110506132631-5wickj6dvrh1dpj6
parent: alexander.nozdrin@oracle.com-20110506132138-46459va9vcbd4nz0
committer: Jorgen Loland <jorgen.loland@oracle.com>
branch nick: mysql-trunk-11765831
timestamp: Fri 2011-05-06 15:26:31 +0200
message:
  BUG#11765831: 'RANGE ACCESS' MAY INCORRECTLY FILTER
                AWAY QUALIFYING ROWS

  Preparation patch (does not include fix for the bug):

   * Extensively document key_or()
   * Remove tab indentations from key_or()
   * Minor code changes like using existing utility functions
     in key_or()