Use warn instead. Those who want style-warn can use a recent UIOP.

Issue: making fare-utils' fine semantics dependent on which underlying version
of UIOP is available causes issues such as in
http://report.quicklisp.org/2017-01-12/failure-report/lisp-interface-library.html

Add a test, update .asd file.

Checked that noone in Quicklisp seems to be using it.

Rename ERROR-BEHAVIOUR to ERROR-BEHAVIOR, as per Google Common Lisp Guidelines.

Deactivate some stateful datastructures that depend on interface;
probably nobody uses them, and they ought to be merged into cl-containers or such.