The macro that opts out of `std::ranges::` functionality is called
`_LIBCPP_HAS_NO_INCOMPLETE_RANGES`, and is unrelated to this macro
which is specifically about _compiler_ support for the _syntax_.
The only non-mechanical diff here is in `<__config>`.
Differential Revision: https://reviews.llvm.org/D118507
The `insert_iterator::iter` member is defined as `Container::iterator` but
the standard requires `iter` to be defined in terms of `ranges::iterator_t` as
of C++20. So, if in C++20 or later, define the `iter` member as
`ranges::iterator_t`.
Original patch by Joe Loser!
Differential Revision: https://reviews.llvm.org/D108575
