I posted an update in the last mailing, preprint available at
https://isocpp.org/files/papers/P1949R3.html

The substantive change is the wording graciously provided by Jens adding a
new production pp-identifier and using it to mark the transition to
identifiers that must be in NFC form.

I hope this doesn't need extensive discussion, and I'd like to get this
back to EWG for review.