[R6RS] action items from today's call

[Anton van Straaten]

> It would help if each of us emailed the group when we complete
> our assigned response updates.

I've committed updates to the following responses:

18 : script exit codes will be dealt with in the script appendix
68 : agreeing with the comment
78 : clarified the vector-map and vector-for-each API
96 : updated to reflect hash table API changes

Anton