find_class(): We no longer mask all exceptions[1] by transforming them
into SystemError. The latter is definitely not the right thing to do,
so we let any exceptions that occur in the PyObject_GetAttr() call to
simply propagate up if they occur.
[1] Note that pickle only masked ImportError, KeyError, and
AttributeError, but cPickle masked all exceptions.
This gives mmap() on Windows the ability to create read-only, write-
through and copy-on-write mmaps. A new keyword argument is introduced
because the mmap() signatures diverged between Windows and Unix, so
while they (now) both support this functionality, there wasn't a way to
spell it in a common way without introducing a new spelling gimmick.
The old spellings are still accepted, so there isn't a backward-
compatibility issue here.
objects to save in gc.garbage. This should be the last change needed to
fix SF bug 477059: "__del__ on new classes vs. GC".
Note that this change slightly changes the behavior of the collector.
Before, if a cycle was found that contained instances with __del__
methods then all instance objects in that cycle were saved in
gc.garbage. Now, only objects with __del__ methods are saved in
gc.garbage.
