bug#68244: hash-table improvements

[Eli Zaretskii]

> From: Mattias Engdegård <mattias.engdegard@gmail.com>
> Date: Sat, 6 Jan 2024 12:34:05 +0100
> Cc: 68244@debbugs.gnu.org,
>  Eli Zaretskii <eliz@gnu.org>,
>  Stefan Monnier <monnier@iro.umontreal.ca>
> 
> Buffer memory is indeed treated differently and does not advance the GC clock 
> as far as I can tell. Presumably the reasoning is that buffer size changes 
> make a poor proxy for object deaths.

Buffer memory is usually allocated via mmap (nowadays, implicitly by
libc), which is why it is treated differently.