[tex-live] xdvipdfmx: tounicode entries for ligatures missing in pdf

[Karl Berry]

Hi Ulrike,

    in the newer pdf a mapping for the ligature is missing:

I can reproduce the problem (xelatex-tl18 fails, xelatex-17 works,
lualatex works with both 17 and 18).

I don't know the ultimate source of the bug, as so much has changed. I
posted the report here in hopes the latexers will investigate further
(sorry to shunt it off to you guys ...):
https://github.com/latex3/graphics-def/issues/17

Best,
Karl