[libcxx-commits] [libcxx] [libc++] Split the PSTL configuration macros into a separate header (PR #205531)

[Louis Dionne via libcxx-commits]

https://github.com/ldionne approved this pull request.

LGTM but I think there's some dead code in the frozen 03 headers that can be removed

https://github.com/llvm/llvm-project/pull/205531