Implement WG21 P2156R1/WG14 N2557 on duplicate attributes
These proposals make the same changes to both C++ and C and remove a
restriction on standard attributes appearing multiple times in the same
attribute list.
We could warn on the duplicate attributes, but do not. This is for
consistency as we do not warn on attributes duplicated within the
attribute specifier sequence. If we want to warn on duplicated
standard attributes, we should do so both for both situations:
[[foo, foo]] and [[foo]][[foo]].
GitOrigin-RevId: 62328f2f29b432dadbd327ff91ba3914c478e3fc
11 files changed
