All supported compilers that support C++20 now support concepts. So, remove
`_LIB_LIBCPP_HAS_NO_CONCEPTS` in favor of `_LIBCPP_STD_VER > 17`. Similarly in
the tests, remove `// UNSUPPORTED: libcpp-no-concepts`.
Differential Revision: https://reviews.llvm.org/D121528
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
C++20 revised the definition of what it means to be an iterator. While
all _Cpp17InputIterators_ satisfy `std::input_iterator`, the reverse
isn't true. D100271 introduces a new test adaptor to accommodate this
new definition (`cpp20_input_iterator`).
In order to help readers immediately distinguish which input iterator
adaptor is _Cpp17InputIterator_, the current `input_iterator` adaptor
has been prefixed with `cpp17_`.
Differential Revision: https://reviews.llvm.org/D101242
* `std::ranges::range`
* `std::ranges::sentinel_t`
* `std::ranges::range_difference_t`
* `std::ranges::range_value_t`
* `std::ranges::range_reference_t`
* `std::ranges::range_rvalue_reference_t`
* `std::ranges::common_range`
`range_size_t` depends on `sized_range` and will be added alongside it.
Implements parts of:
* P0896R4 The One Ranges Proposal`
Depends on D100255.
Differential Revision: https://reviews.llvm.org/D100269
