changes in sbcl-1.1.18 relative to sbcl-1.1.17:
* optimization: COERCE is now more effecient for more cases when the type is
known at compile-time.
(lp#1309815)
* bug fix: correctly inherit condition initforms. (lp#1300904)
* bug fix: properly pprint literal functions inside nested lists.
(lp#1300716)
* bug fix: more-correctly handle array-type unity (broken for ages, causing
compilation problems since 1.1.13.x due to smarter TYPEP type propagation,
reported by jasom in #lisp).