Merge changes from python-ldap 2.5.1

[tiran]

This merges 2.5.1 release:

Mandatory prerequisites:
- Python 2.7.x
- pyasn1 0.3.7+ and pyasn1_modules 0.1.5+

Modules/
* removed unused code schema.c

Lib/
* ldap.__version__, ldap.__author__ and ldap.__license__ now
  imported from new sub-module ldap.pkginfo also to setup.py
* Added safety assertion when importing _ldap:
  ldap.pkginfo.__version__ must match _ldap.__version__
* removed stand-alone module dsml
* slapdtest.SlapdObject.restart() just restarts slapd
  without cleaning any data
* Compability changes for pyasn1 0.3.x or newer
  (thanks to Ilya Etingof and Christian Heimes)
* The methods SSSResponseControl.decodeControlValue() and
  VLVResponseControl.decodeControlValue() now follow the coding
  convention to use camel-cased ASN.1 name as class attribute name.
  The old class names are still set for back-ward compability
  but should not be used in new code because they might be removed
  in a later release.
* removed SSSRequestControl from ldap.controls.KNOWN_RESPONSE_CONTROLS

Tests/
* added explicit reconnect tests for ReconnectLDAPObject

[hroncok]

Sorry, i won't be able to review this any time soon.

[encukou]

I think we need to release 2.4.45 first, so there's an up-to-date version that works with the old pyasn.

[encukou]

LGTM. Let's merge after I get 2.4.45 out (today or tomorrow), and include the fix for https://github.com/pyldap/pyldap/pull/135 .