Fixed a problem in tail-must-be-proper-list-with-end revealed by latest tests.
Fixed a problem in tail-must-be-proper-list-with-end revealed
by latest tests.

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