bug#70137: 30.0.50; pp-macroexpand-last-sexp buffers should turn lexical binding on

[Eli Zaretskii]

> From: Augusto Stoffel <arstoffel@gmail.com>
> Date: Tue, 02 Apr 2024 08:01:18 +0200
> 
> If you call pp-macroexpand-last-sexp in a buffer with lexical binding,
> the resulting *Pp Macroexpand Output* buffer has lexical binding turned
> off.
> 
> The problem with this is that if you now go the *Pp Macroexpand Output*
> buffer and call pp-macroexpand-last-sexp again, this second macro
> expansion step may not reflect what would happen in the original buffer;
> I don't recall an example, but some macros expand differently in the two
> variable scoping modes.

Adding Stefan.