+ ** literal spaces directly after ~<Newline> directives within a
+ format-logical-block (~:< ~@:>) do not induce :FILL-style
+ conditional newlines.
+ ** PRINT-UNREADABLE-OBJECT inserts spaces as specified (and only
+ as specified: it no longer includes conditional newlines).
+ ** PRINC-TO-STRING binds *PRINT-READABLY* to NIL (as well as
+ *PRINT-ESCAPE*).
+ ** PPRINT-LOGICAL-BLOCK signals a TYPE-ERROR if its :PREFIX or
+ :PER-LINE-PREFIX argument does not evaluate to a string.