Wrapper to indicate a C local variable declaration in an mv-let that side-effects 3 additional variables.
See atc-let-designations.
Macro: declar3
(defmacro declar3 (x) (cons 'mv-let (cons '(*0 *1 *2 *3) (cons x '((mv (declar *0) *1 *2 *3))))))
