Replaced PyLong_{As,From}{Unsigned,}LongLong guts with calls
    to _PyLong_{As,From}ByteArray.
_testcapimodule.c:
    Added strong tests of PyLong_{As,From}{Unsigned,}LongLong.

Fixes SF bug #432552 PyLong_AsLongLong() problems.
Possible bugfix candidate, but the fix relies on code added to longobject
to support the new q/Q structmodule format codes.