[PATCHv2] malloc: Make sure tcache_key is odd enough

[Florian Weimer]

* Wilco Dijkstra:

> Hi,
>
>> I thought that exactly 80 columns was acceptable, but the GNU
>> standards disagree:
>>
>> | Please keep the length of source lines to 79 characters or less, for
>> | maximum readability in the widest range of environments.
>> 
>> <https://www.gnu.org/prep/standards/html_node/Formatting.html>
>
> We should really increase that limit a little. It's 2025 after all,
> not 1980 - everyone has huge screens...

Some of us fit multiple terminal/editor windows side-by-side on larger
screen, or use portrait mode.

If we increase it, the actual rule should be something like “the
non-whitespace region of the line should cover at most 72 columns” or
something like that because readability suffers for very long lines.
And the line that triggered this discussion would still not meet that
requirement (because the comment was not deeply indented).