Define a condition that is signaled when a list circular.
Define a condition that is signaled when a list circular.

Make the butlast and nbutlast functions detect circular lists.

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