[issue22013] Add at least minimal support for thread groups

[Raymond Hettinger]

Changes by Raymond Hettinger <raymond.hettinger at gmail.com>:


----------
nosy: +Christian.Tismer, aleax, kristjan.jonsson, lemburg

_______________________________________
Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue22013>
_______________________________________