This is Neil's fix for SF bug 535905 (Evil Trashcan and GC interaction).
The fix makes it possible to call PyObject_GC_UnTrack() more than once
on the same object, and then move the PyObject_GC_UnTrack() call to
*before* the trashcan code is invoked.
BUGFIX CANDIDATE!
Bugfix candidate.
tb_displayline(): the sprintf format was choking off the file name, but
used plain %s for the function name (which can be arbitrarily long).
Limit both to 500 chars max.
For more comments, read the patches@python.org archives.
For documentation read the comments in mymalloc.h and objimpl.h.
(This is not exactly what Vladimir posted to the patches list; I've
made a few changes, and Vladimir sent me a fix in private email for a
problem that only occurs in debug mode. I'm also holding back on his
change to main.c, which seems unnecessary to me.)
Added wrapping macros to dictobject.c, listobject.c, tupleobject.c,
frameobject.c, traceback.c that safely prevends core dumps
on stack overflow. Macros and functions in object.c, object.h.
The method is an "elevator destructor" that turns cascading
deletes into tail recursive behavior when some limit is hit.
bltinmodule.c: fixed coerce() nightmare in ternary pow().
modsupport.c (initmodule2): pass METH_FREENAME flag to newmethodobject().
pythonrun.c: move flushline() into and around print_error().
