Author: Zoffix Znet <zoffixz...@users.noreply.github.com>
Date: 2016-10-14 (Fri, 14 Oct 2016)
Remove Signature/Attribute Defaults Based on Definedness
Per discussion with pmchaud, this feature can be added to current rakudo,
without needing a 6.d (as it doesn't interfere with anything), and should first
be implemented as a user-space module for experimentation.