S9fES  (reverse! list)  ==>  list

Reverse LIST in situ, thereby destroying the original list.
Return the reversed list. REVERSE! is much more efficient
than REVERSE, but does not preserve the original list. When
porting S9fES programs, REVERSE! can be replaced by REVERSE.

NOTE: When reversing a list that is bound to a symbol, the
symbol will thereafter be bound to the *last* member of the
list.

(define x '(1 2 3 4 5))

(reverse! x)  ==>  (5 4 3 2 1)
x             ==>  (1)
