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
Implement LWG3549 by making `view_interface` not inherit from `view_base`. Types
are still views if they have a public and unambiguous derivation from
`view_interface`, so adjust the `enable_view` machinery as such to account for
that.
Differential Revision: https://reviews.llvm.org/D117714