bug#39554: 27.0.50; cairo not composing sequences

[Eli Zaretskii]

> From: James Cloos <cloos@jhcloos.com>
> Cc: 39554@debbugs.gnu.org
> Date: Thu, 13 Feb 2020 15:16:39 -0500
> 
> It does work correctly when i turn on variable-pitch-mode, which here is
> set to use DejaVu Serif.
> 
> But xft does fine with DejaVu Sans Mono.
> 
> This bug remains a regression and requires a fix.

I don't think I agree.  This font has problems with combining accents,
see this discussion:

  https://lists.freedesktop.org/archives/harfbuzz/2019-August/007422.html