Simplify change of 41cc9eb: don't over-call SWANK on REPL calls.

* contrib/slime-repl.el (slime-repl-eval-string): simplify change of
2014-01-30; don't remotely call SWANK:SET-REPL-VARIABLES on
acknowledgement.

* contrib/swank-repl.lisp (set-repl-variables): Deleted.
(*repl-set-variables-function*): Deleted, not needed for now.
(repl-eval): Set *, + and / variables saved from last call just
before the EVAL-REGION that might use them.