[gcc r15-809] libstdc++: Implement ranges::concat_view from P2542R7

https://gcc.gnu.org/g:66d2a76dcf625f8dbe43d3c512e9c43f588fdc25 commit r15-809-g66d2a76dcf625f8dbe43d3c512e9c43f588fdc25 Author: Patrick Palka Date: Thu May 23 18:03:56 2024 -0400 libstdc++: Implement ranges::concat_view from P2542R7 libstdc++-v3/ChangeLog: *

[gcc r14-9756] libstdc++: Allow adjacent __maybe_present_t fields to overlap

https://gcc.gnu.org/g:0e64bbb8823f7b3757befc878ed177dfb59943d1 commit r14-9756-g0e64bbb8823f7b3757befc878ed177dfb59943d1 Author: Patrick Palka Date: Tue Apr 2 13:07:07 2024 -0400 libstdc++: Allow adjacent __maybe_present_t fields to overlap Currently __maybe_present_t maps to the