Merge branch 'tb/macos-iconv-workarounds'

The iconv library on macOS fails to correctly handle stateful ISO/IEC 2022 encoded strings. Work it around instead of replacing it wholesale from homebrew. * tb/macos-iconv-workarounds: utf8.c: enable workaround for iconv under macOS 14/15 utf8.c: prepare workaround for iconv under macOS 14/15