bug#56739: 29.0.50; `cl-psetq' and `cl-psetf' fail to recognize symbol macros

[Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

> The following form produces (2 2) due to the failure of detecting
> dependencies involving symbol macros.
>
> (cl-symbol-macrolet ((c a))
>   (let ((a 1) (b 2))
>     (cl-psetq a b
>               b c)
>     (list a b)))

BTW, another way to get similar problems is with `defvaralias`:

    (defvaralias 'my-c 'my-a)
    (defvar my-a 1)

    (let ((b 2))
      (cl-psetq my-a b
                b my-c)
      (list my-a b))

We should probably introduce a `(macroexp|cl)--simple-var-p` test to
catch the various cases where symbols aren't simple variables.

Another thing that might be worth digging into is how important is that
`cl-psetf` optimization for lexical variables (remember: this was
written back in the days of dynamic scoping and Mattias has made some
improvements to the compiler which may render this optimization
redundant inside the macro itself.


        Stefan