bug#44784: Combining accent is not combining

[Eli Zaretskii]

Btw, the report by Emacs 27's "C-u C-x =", viz.:

  Composed with the following character(s) "́" using this font:
    xfthb:-PfEd-DejaVu Sans Mono-normal-normal-normal-*-22-*-*-*-m-0-iso10646-1
  by these glyphs:
    [0 1 1071 878 13 0 13 16 0 nil]
    [0 1 769 649 13 4 11 17 -13 [0 0 0]]

explicitly says that character composition _did_ happen here, it's
just the display that is broken.  And I guess that moving point to
these characters will show a "fat" cursor that includes both the base
character and the accent, once again showing that Emacs did compose
the accent with the preceding character.