Final update: we decided it was cleaner to just update Foundation now rather
than building with a separate branch and having to work out those dependencies,
so essentially nothing will change. The pull request has been landed but is
still planned to have a full post-commit review at a later date
Update: we've created the master-before-optional-pointers branch at ff373e9,
but run into some complications putting this plan into action. (Specifically, I
forgot that SwiftPM depends on XCTest for its test cases, and that XCTest of
course depends on Foundation.) I'll send another message tomor
