Log Message:
Changes 2.4.20:

* New wrapping of OpenLDAP's function ldap_sasl_bind_s() allows
  to intercept the SASL handshake

Modules/
* Added exceptions ldap.VLV_ERROR, ldap.X_PROXY_AUTHZ_FAILURE and
  ldap.AUTH_METHOD_NOT_SUPPORTED

Lib/
* Abandoned old syntax when raising ValueError in modules ldif and
  ldapurl, more information in some exceptions.
* ldap.ldapobject.LDAPObject:
  New convenience methods for SASL GSSAPI or EXTERNAL binds
* Refactored parts in ldif.LDIFParser:
  - New class attributes line_counter and byte_counter contain
    amount of LDIF data read so far
  - Renamed some internally used methods
  - Added support for parsing change records currently limited to
    changetype: modify
  - New separate methods parse_entry_records() (also called by parse())
    and parse_change_records()
  - Stricter order checking of dn:, changetype:, etc.
  - Removed non-existent 'AttrTypeandValueLDIF' from ldif.__all__
* New mix-in class ldap.controls.openldap.SearchNoOpMixIn
  adds convience method noop_search_st() to LDAPObject class
* Added new modules which implement the control classes
  for Virtual List View (see draft-ietf-ldapext-ldapv3-vlv) and
  Server-side Sorting (see RFC 2891)
  Note: This is still experimental! Even the API can change later.