Add option --with-unicode9 on devel and head for Unicode 9 character
width support. The option is not enabled by default because support is
required from both the shell and the terminal emulator; disparity could
cause garbled output. A simple test case is "echo 👍1👍2👍3" at the
prompt:
- If neither zsh nor the terminal emulator has Unicode 9 width tables,
each digit will overlap with its previous emoji, but editing will
still be very much possible;
- If zsh has Unicode 9 width tables but the terminal emulator doesn't,
the string will be garbled and editing will be very difficult;
- If both zsh and the terminal emulator have Unicode 9 width tables,
output will be correct and editing won't be hindered.
Terminal.app currently doesn't support Unicode 9, making the option a
tough sell as default. For the record, iTerm2 nightlies since 08/08/2016
have opt-in Unicode 9 width support and version switching. See
https://gitlab.com/gnachman/iterm2/wikis/unicodeversionswitching.