cl-loop's "with" destructuring-bind looks broken

[Tomohiro Matsuyama]

Hi,

I have faced an issue on 24.3.90.2 when using my extension that
includes an expression like:

    (cl-loop with (a b c) = '(1 2 3) return (+ a b c))

This expression causes an error:

    Attempt to set a constant symbol: nil

On a stable release, at least 24.3.1, it works fine and evalutes to 6.

ANSI Common Lisp allows such destructuring-bind with "with" clause, by
the way.

Regards,
Tomohiro