For reference:

How to call script main in R7RS mode? #563
https://github.com/shirok/Gauche/issues/563

This is probably where concrete design work started, also concerns SRFI
22 and `scheme-script` symlinks.

Experimental command-lines module #640
https://github.com/shirok/Gauche/pull/640

This is the first draft implementation, now replaced by a better one by
Shiro.