Highlights:
* ``LDAPError`` now contains additional fields, such as ctrls, result, msgid
* ``passwd_s`` can now extract the newly generated password
* LDAP connections can now be made from a file descriptor

This release is tested on Python 3.8, and the beta of Python 3.9.

The following undocumented functions are deprecated and scheduled for removal:
- ``ldap.cidict.strlist_intersection``
- ``ldap.cidict.strlist_minus``
- ``ldap.cidict.strlist_union``

Modules/
* Ensure ReconnectLDAPObject is not left in an inconsistent state after
  a reconnection timeout
* Syncrepl now correctly parses SyncInfoMessage when the message is a syncIdSet
* Release GIL around global get/set option call
* Do not leak serverctrls in result functions
* Don't overallocate memory in attrs_from_List()
* Fix thread support check for Python 3
* With OpenLDAP 2.4.48, use the new header openldap.h

Lib/
* Fix some edge cases regarding quoting in the schema tokenizer
* Fix escaping a single space in ldap.escape_dn_chars
* Fix string formatting in ldap.compare_ext_s
* Prefer iterating dict instead of calling dict.keys()

Doc/
* Clarify the relationship between initialize() and LDAPObject()
* Improve documentation of TLS options
* Update FAQ to include Samba AD-DC error message
  "Operation unavailable without authentication"
* Fix several incorrect examples and demos
  (but note that these are not yet tested)
* Update Debian installation instructions for Debian Buster
* Typo fixes in docs and docstrings

Test/
* Test and document error cases in ldap.compare_s
* Test if reconnection is done after connection loss
* Make test certificates valid for the far future
* Use slapd -Tt instead of slaptest

Infrastructure:
* Mark the LICENCE file as a license for setuptools
* Use "unittest discover" rather than "setup.py test" to run tests