Fix `lset=` in SRFI 1 / `(scheme list)` (small issue, side-effects only)

[jpellegrini]

The reference (sample) implementation had a bug that reversed the arguments to =. The implementation has been corrected to match the SRFI text, and we do so in STklos also.

See: https://srfi.schemers.org/srfi-1/srfi-1.html#lset%3D-element-equality-order

The difference in behavior is only for side-effects. It can be seen in this example:

;; OLD version of lset=
scheme/list> (lset= (lambda (x y) (print x) (= x y)) '(1 2 ) '(1 2 ))
1
2
2
1
2      ;; <= HERE!
2

;; NEW version of lset=
scheme/list> (lset=-new (lambda (x y) (print x) (= x y)) '(1 2 ) '(1 2 ))
1
2
2
1
1      ;; <= HERE!
2

[egallesio]

Thanks for your vigilance @jpellegini. Merged