bug#45333: complex command history should not save optional nil parameters

[Stefan Monnier]

> For 2), I think we could stop upcasing arguments and adjust callers --
> but old .elc files would still have upcased arguments until recompiled.

`C-h o` wants them upcased, eldoc wants them downcased.
So far we have prioritized `C-h o`.  Maybe eldoc shouldn't downcase :-)

> For 1), we could also stash the actual arglist in addition to the
> advertised calling convention into .elc/DOC (i.e., two (fn ...) forms,
> for instance).

Why/when do we need the non-advertized arglist?


        Stefan