Bug#873315: firefox-esr does not print typographic ligatures fi and fl

[Hartmut Buhrmester]

Furthermore, the missing ligatures are not replaced with some "weird 
character", but with an inverted question mark ¿ as used in Spanish.

Thus, Zertifikat is displayed as Zerti¿kat (see attached screenshot 
replacement-character.png).

Regards,
Hartmut Buhrmester