Also SF patch 843455.
This is a critical bugfix.
I'll backport to 2.3 maint, but not beyond that. The bugs this fixes
have been there since weakrefs were introduced.
* Install the unittests, docs, newsitem, include file, and makefile update.
* Exercise the new functions whereever sets.py was being used.
Includes the docs for libfuncs.tex. Separate docs for the types are
forthcoming.
subtype_dealloc(): This left the dying object exposed to gc, so that
if cyclic gc triggered during the weakref callback, gc tried to delete
the dying object a second time. That's a disaster. subtype_dealloc()
had a (I hope!) unique problem here, as every normal dealloc routine
untracks the object (from gc) before fiddling with weakrefs etc. But
subtype_dealloc has obscure technical reasons for re-registering the
dying object with gc (already explained in a large comment block at
the bottom of the function).
The fix amounts to simply refraining from reregistering the dying object
with gc until after the weakref callback (if any) has been called.
This is a critical bug (hard to predict, and causes seemingly random
memory corruption when it occurs). I'll backport it to 2.3 later.
charmaptranslate_makespace() allocated more memory than required for the
next replacement but didn't remember that fact, so memory size was growing
exponentially every time a replacement string is longer that one character.
This fixes SF bug #828737.
