Revert revisions:

Revert revisions:

46640 Patch #1454481:  Make thread stack size runtime tunable.
46647 Markup fix

The first is causing many buildbots to fail test runs, and there
are multiple causes with seemingly no immediate prospects for
repairing them.  See python-dev discussion.

Note that a branch can (and should) be created for resolving these
problems, like

svn copy svn+ssh://svn.python.org/python/trunk -r46640 svn+ssh://svn.python.org/python/branches/NEW_BRANCH

followed by merging rev 46647 to the new branch.