bug#29866: 27.0.50; cl-loop: Calculate the array length just once

[Stefan Monnier]

> While studying this code I found easier to hack if we use gensym's
> instead of make-symbol; otherwise, the code creates several symbols with
> the same printed representation "--cl-var--".  For example, with current
> code you can read expansions with something like:

I always (setq print-gensym t print-circle t)


        Stefan