[PATCH v5] manual: Document clock_nanosleep

[Maciej W. Rozycki]

On Fri, 30 May 2025, Arjun Shankar wrote:

> >  OK.  You could've justified the paragraph such that the line break is in
> > the middle of @xref just as I did (and the whole paragraph would then line
> > up more nicely in the source form), but I'm not going to insist (OK if you
> > choose to after all at the commit push time too).
> 
> I wasn't quite sure if a line break would work and I was too lazy to
> try to find out if it would. For this time, I'm going to push without
> changes so the version ack'd is identical to the one pushed.

 We have existing use cases throughout the manual, it's easy to check even 
without rebuilding (and I did double-check too).

  Maciej