Add support of the Libevent extra API

Packages describing “extra” as local USE flag

Package “extra” Flag Description
dev-php/pecl-event Add support of the Libevent extra API
media-fonts/noto Install full upstream font set including condensed, semi-bold, extra-light variants
sys-devel/clang Build extra tools (clangd, clang-tidy and a few more)
sys-block/f3 Build the additional f3probe, f3brew and f3fix utility (requires sys-block/parted and virtual/udev)
media-video/pipewire Build pw-cat/pw-play/pw-record
app-i18n/rime-data Install extra packages
app-shells/nushell Enable less stable or less common commands
app-text/texlive Add support for extra TeXLive packages

All packages providing a “extra” USE flag (5)