CWG2733 Applying [[maybe_unused]] to a label

[jensmaurer]

Both gcc and clang accept [[maybe_unused]] on an identifier label.

This seems to be a small extension that improves consistency of the language; EWG is asked to approve.

See CWG2733 for details including CWG-approved wording.

[erichkeane]

EWG discussed CWG2733 during the Tuesday Morning session in Kona. The following poll was taken.

CWG2733 "Applying [[maybe_unused]] to a label" accept the proposed resolution, forward to CWG for inclusion in C++26.

SF	F	N	A	SA
5	12	3	0	0

Result: Consensus

[jensmaurer]

CWG 2023-11-07: Approved.