Slightly incompatible changes in next world

[Moon at MIT-AI (David A. Moon)]

1. The system will start using the variables ++, **, +++, ***, and //.  These
   symbols are not global now, but will be in the next system.
   // will hold the list of multiple values of the last form; like * but you
   get a list of the values rather than just the first.
   ++ will hold the previous value of +, and +++ the value before that.
   ** will hold the previous value of *, and *** the value before that.
   These are not a substitute for a full-blown history feature, but in their
   simplicity should make interacting with the read-eval-print loop easier.
2. If formerly you had (format x "~{~S~}" y), now you must say
   (format x "~{~S~^, ~}" y).  If you never heard of this, don't worry
   about it.
3. The system will thrash a little less.  Let me know if this inconveniences
   anyone.