[CM] R7RS support

[mike at eggheadgames.com]

> Do you know if there is a test suite for the r7rs additions?

There are a lot of tests in the chibi-scheme repo, e.g.:

https://github.com/ashinn/chibi-scheme/blob/master/tests/r7rs-tests.scm

I’m not sure if that’s what you were seeking, but hopefully it’s 
useful. It appears to cover many R7RS features. However other files in 
that directory appear at first glance to test overlapping areas as well.

Thanks again for your responses Bill!

Cheers, Michael