[$] A new parser for CPython

A new parser for the CPython implementation of the Python language has beenin the works for a while, but the announcement of a Python Enhancement Proposal (PEP) for it indicates thatwe may see it fairly soon. The intent is to add the parser, and make it the default for Python 3.9,which is due in October.If that plan holds, the current parser will not be going away for anotheryear or so after that. The change should go completelyunnoticed within the community; the benefits are mainly for the CPython coredevelopers in the form of easier maintenance.