Fix plus function in core.lisp
Fix plus function in core.lisp

Testing that the plus function was incorrect was accomplished as such:

(label z (quote (z)))
(label succ (lambda (x) (cons (quote s) x)))
((plus one one) succ z)

The result expected was (s s z), however the interpreter crashed.

readevalprintlove/lithp,magomsk/lithp,fogus/lithp,magomsk/lithp,readevalprintlove/lithp,fogus/lithp,magomsk/lithp,fogus/lithp,readevalprintlove/lithp