Python 3.9 brings the `cache` decorator, which is equivalent to our own
`memoize`. Replace the latter in all remaining places and use `cache`
instead.

Also delete unused `mp_forking` and "async" decorators. The latter can
be achieved via the `concurrent.futures` module.

 - Protect against container changing during iteration.

 - iteritems
 - has_key
 - text/binary file formats
 - string module

Initial python3 port.  For now, just what's needed for basic
athena/configuration jobs.  Avoid implicit relative imports.

Release memory in PerfMonSvc::postFinalize, to reduce noise in leak-checking. (PerfMonComps-00-25-07)

	* Tagging PerfMonComps-00-25-07.
	* src/PerfMonSvc.cxx (postFinalize): Release memory used by
	m_ntuple here, to cut down noise in leak-checking.

2015-01-22  Antonio Limosani  <antonio.limosani@sydney.edu.au>

	* Tagging PerfMonComps-00-25-06.
	* Bug fix. Fitting range for mem-leak estimation adjusted.

2015-01-16  Antonio Limosani  <antonio.limosani@sydney.edu.au>

	* Tagging PerfMonComps-00-25-05.
	* Changing memleak fit regions from (20 to 50,51+) to (20 to 100,100+) event ranges