Patch #1731049: make threading.py use a proper "raise" when checking internal state, rather than assert statements (which get stripped out by -O).

64-bit boxes.  I have no idea what the ctypes docs mean
by "integers", and blind-guessing here that it intended to
mean the signed C "int" type, in which case perhaps I can
repair this by feeding the thread id argument to type
ctypes.c_long().

Also made the worker thread daemonic, so it doesn't hang
Python shutdown if the test continues to fail.

PyThreadState_SetAsyncExc():  internal correctness changes wrt
refcount safety and deadlock avoidance.  Also added a basic test
case (relying on ctypes) and repaired the docs.

platforms that don't support changing thread stack size.

to pass reliably on the one buildbot that insists on
more than 32kB of thread stack.

Heavily revised, comprising revisions:
46640 - original trunk revision (backed out in r46655)
46647 - markup fix (backed out in r46655)
46692:46918 merged from branch aimacintyre-sf1454481

branch tested on buildbots (Windows buildbots had problems
not related to these changes).

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.

test_threading.test_foreign_thread():  new test does a basic check that
"foreign" threads can using the threading module, and that they create
a _DummyThread instance in at least one use case.  This isn't a very
good test, since a thread created by thread.start_new_thread() isn't
particularly "foreign".

does what it's supposed to do.

imports e.g. test_support must do so using an absolute package name
such as "import test.test_support" or "from test import test_support".

This also updates the README in Lib/test, and gets rid of the
duplicate data dirctory in Lib/test/data (replaced by
Lib/email/test/data).

Now Tim and Jack can have at it. :)

to stdout.  Repaired by not printing at all except in verbose mode.

Made the test about 6x faster -- envelope analysis showed it took time
proportional to the square of the # of tasks.  Now it's linear.