hexchat-plugin has a
print(impl ToString) which is a line-writer. It doesn't support the equivalent of
write_fmt. It'd be nice if
write_line were separate so that our
write_fmt could be
write_line didn't push a newline at the end (altho hexchat doesn't care about a terminating newline, and in fact slightly prefers it, but w/e).
This would be used by