Lay some groundwork for improvements to the connection pool.

  remove unnecessary uldap_connection_cleanup (nothing needed between unbind 
  and remove)

  properly remove rebind callback info when credentials change

  maintain a separate pool for the rebind callback storage so it can be cleared
  when the connection is unbound.

(major bump for util_ldap function removal)



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1081005 13f79535-47bb-0310-9956-ffa450edef68