This check flags code which uses `_LIBCPP_STD_VER` the wrong way, or tries to use `__cplusplus`. It flags cases where we use `_LIBCPP_STD_VER >` instead of `_LIBCPP_STD_VER >=` and where wrong values are used (e.g. `_LIBCPP_STD_VER >= 24`).
Reviewed By: ldionne, #libc
Spies: libcxx-commits
Differential Revision: https://reviews.llvm.org/D144261
Partially implements:
- P1361 Integration of chrono with text formatting
- P2372 Fixing locale handling in chrono formatters
- P1466 Miscellaneous minor fixes for chrono
Depends on D137022
Reviewed By: ldionne, #libc
Differential Revision: https://reviews.llvm.org/D139771