Bug 633168 - Share backend dbEnv with the replication changelog
    
    https://bugzilla.redhat.com/show_bug.cgi?id=633168
    
    Description:
    * cl5_api.c, cl5_api.h
      - fetches dbEnv from backend using slapi_back_get_info.
      - unused macros and DB helper functions and APIs are removed.
    * cl5_config.c
      - local changelog DB related config parameters are removed.
    * Added SLAPI_PLUGIN_BE_PRE_CLOSE_FN and SLAPI_PLUGIN_BE_POST_OPEN_FN to
      close changelog DB before dbEnv is closed and to open changelog DB after
      dbEnv is opened, respectively.
    * Added slapi APIs slapi_back_get_info and slapi_back_set_info to get/set
      the backend info.
    * back-ldbm
      - db2bak[.pl] and bak2db[.pl] backs up and restores the database files
        including changelog db.
      - changelog dir is backed up in <backupdir>/.repl_changelog_backup.
      - underlying implementation ldbm_back_get_info for slapi_back_get_info
        is added.
    * Added an upgrade script 81changelog.pl
    
    See also:
    http://directory.fedoraproject.org/wiki/Move_changelog