Message 274576 - Python tracker

Nosy list copied from #23085.

Here's a patch that deprecates building _ctypes with the bundled copy of libffi (Modules/_ctypes/libffi/).  The default on all platforms (other than Windows) is now to use a system copy of libffi; use the '--without-system-ffi' flag to ./configure to use the bundled copy.  On non-Darwin platforms, a warning will be emitted noting that Modules/_ctypes/libffi will not be distributed with 3.7.