warnings under -3.

Issue 643841: better documentation of the special method lookup process, especially for new-style classes. Also removes the warnings about not being authoritative for new-style classes - the language reference actually covers those fairly well now (albeit in a fashion that isn't always particularly easy to follow).

key list data structure in the thread startup path.

This change is a companion to r60148 which already successfully dealt with a
similar issue on thread shutdown.

In particular this loop has been observed happening from this call path:
 #0  in find_key ()
 #1  in PyThread_set_key_value ()
 #2  in _PyGILState_NoteThreadState ()
 #3  in PyThreadState_New ()
 #4  in t_bootstrap ()
 #5  in pthread_start_thread ()

I don't know how this happens but it does, *very* rarely.  On more than
one hardware platform.  I have not been able to reproduce it manually.
(A flaky mutex implementation on the system in question is one hypothesis).

As with r60148, the spinning we managed to observe in the wild was due to a
single list element pointing back upon itself.

names with docstring.

and add corresponding tests.
Possible 2.5 backport candidate

of using pipes that cause deadlocks.

while running under -3.

running under -3.

  argument in python 2.5, this broke code that subclassed Popen to include its
  own poll method.  Fixed my moving _deadstate to an _internal_poll method.

warnings when run under -3.

warnings triggered under -3.

package, when run under -3, about using <>.

under -3 through test_xmlrpc.

move from list.sort(cmp=) to key=.

cookielib.

unpacking in parameter lists and using callable(). Found through -3.

urlparse when run under -3.

AttributeError since __slots__ were added to zipfile.ZipInfo in
r46967 two years ago.
Add a warning about the removal of TarFileCompat in Python 3.0.

Tcl command objects.

under -3.

while running under -3.