Add tests for butlast and nbutlast that test for circular lists.
Add tests for butlast and nbutlast that test for circular lists.

clasp-developers/SICL,vtomole/SICL,vtomole/SICL,clasp-developers/SICL,vtomole/SICL,vtomole/SICL,clasp-developers/SICL,clasp-developers/SICL