SRFI 220 is past the 60-day milestone. Do we have what it takes to
achieve consensus on it? If not, I'd rather withdraw it and leave it as
documentation for future work on the topic.

- The current approach, of parsing "#! ..." lines as Scheme code, works
quite well but so far I'm the only one who thinks we should do that.

- Taking "#! ..." lines as raw strings and parsing each idiosyncratic
syntax in a hook procedure works, and I'm willing to switch to that if
people agree to it.

- Using characters other than "#!" has been suggested. I'm very much in
favor of "#!" since we have it already; Marc N-W thinks it's confusing
to conflate the new meaning of "#! ..." as a line directive with the
existing meanings of directives like "#!r6rs" and Unix shebang lines
like "#! /usr/bin/env fantastic-scheme".