Create a path toward sharing memory from a numpy buffer

I know there is some concern about having the memory aligned.

I didn't know if it needed to be aligned to 16 bits, or 16 bytes.

If you know let me know which it is, I can add a check for it. If you don't want to support this, then that is fine too.

Closes: https://github.com/PyAV-Org/PyAV/issues/1060