As done for std::pair, this defines operator<=> as a non-member function
template and does not alter operator==, as expected to be proposed as
the resolution to an unpublished LWG issue.
Instead of calling std::lexicographical_compare_three_way the <=>
overload is implemented by hand to take advantage of the fact the
element types and array sizes are known to be the same.
* include/bits/cpp_type_traits.h (__is_byte<char8_t>): Add
specialization.
* include/std/array (operator<=>): Likewise.
* testsuite/23_containers/array/comparison_operators/constexpr.cc:
Test three-way comparisons and arrays of unsigned char.
* testsuite/23_containers/array/tuple_interface/get_neg.cc: Adjust
dg-error line numbers.
From-SVN: r278981
3a4cc6281b