changes in sbcl-0.7.12 relative to sbcl-0.7.11:

  * minor incompatible change: code processed by the "interpreter" or
    EVAL now has a compilation optimization policy of (DEBUG 2)
    (changed from (DEBUG 1)) to improve debuggability of interactive
    development, and to allow the use of the debug RETURN command in
    such code.
  * an experimental implementation of the RETURN command for the
    debugger has been included.  (thanks to Frederik Kuivinen)
  * fixed bug 62: constraints were not propagated into a loop.
  * fixed bug in embedded calls of SORT (reported and investigated by
    Wolfgang Jenkner).
  * fixed some bugs revealed by Paul Dietz' test suite:
    ** printing and reading of arrays with some dimensions having
       length 0 (thanks to Gerd Moellmann);
    ** BOA constructor with &AUX argument without a default value does
       not cause a type error;
    ** CONSTANTP now returns true for all self-evaluating objects.