bug#32746: setitimer API is obsolescent

[Eli Zaretskii <eliz@gnu.org>]

> From: Paul Eggert <eggert@cs.ucla.edu>
> Date: Sun, 16 Sep 2018 13:32:33 -0700
> 
> POSIX made the getitimer/setitimer API obsolescent a decade ago, and now's a 
> good time for Emacs to rely on the current timer_gettime/timer_settime API 
> instead. I've proposed patches for this in Bug#32746. If you know a platform 
> that is a current porting target of Emacs and lacks timer_gettime/timer_settime 
> but has getitimer/setitimer, please send email to <32746@debbugs.gnu.org> about 
> it. (MS-Windows lacks both APIs; the proposed patches attempt to address that 
> special case.)

Thanks, I will send my comments to the MS-Windows part of the patch in
a moment.

However, I think it might be too early to remove support for
setitimer, because some platforms have problems with it.  AFAIK, macOS
and some *BSD version either don't have that family or have buggy
implementations.

Supporting the old APIs only needs a couple of #ifdef's in 3 files, so
it doesn't sound like a terrible maintenance burden.

Btw, it would be good to have some tests for these facilities, as
currently we don't have any practical means to make sure we don't
introduce bugs when we switch to alternative APIs.