Fix crash caused by 8c1385205a35
(thanks Arfrever for reporting).
Fix crash caused by 8c1385205a35
(thanks Arfrever for reporting).
#17798: Allow IDLE to edit new files when specified on command line.
#17798: merge with 3.3.
Issue #15528: Add weakref.finalize to support finalization using
weakref callbacks.
Backout 2e446e87ac5b; it breaks the unix buildbots.
Issue #17094: Clear stale thread states after fork().

Note that this is a potentially disruptive change since it may
release some system resources which would otherwise remain
perpetually alive (e.g. database connections kept in thread-local
storage).
Issue #15528: Add weakref.finalize to support finalization using
weakref callbacks.

This is 2e446e87ac5b except that collections/__init__.py has been
modified to import proxy from _weakref instead of weakref.  This
eliminates an import cycle which seems to cause a problem on Unix but
not Windows.