bug#65491: [PATCH] Improve performance allocating vectors

[Eli Zaretskii]

> From: Mattias Engdegård <mattias.engdegard@gmail.com>
> Date: Sat, 16 Sep 2023 16:58:01 +0200
> Cc: 65491@debbugs.gnu.org,
>  Eli Zaretskii <eliz@gnu.org>
> 
> I also pushed two small changes that were essential to working with the code 
> so we might just as well have them in now: b1881d7dab (fix a static 
> assertion) and 056c99a34c (better Lisp_Object untagging).

The latter one completely broke the 32-bit build --with-wide-int, most
probably because the last argument to XUNTAG is frequently a pointer
to a 64-bit type, where uintptr_t is only 32-bit wide.  As result, I
cannot even compile Emacs: each C file emits the same warnings, which
fill up my screen in a matter of milliseconds.

Please try to fix this ASAP, as it makes me unable to work on master.