[Development] QFont: change substitutions

[Jan Sundermeyer]

Qt uses substitute fonts when a character is not present in the
principal font.
Apparently the substitute fonts are not always to the users taste, so
they like to change the substitution.

QT offers a function for it (QFont::substitutes), however it would be
tedious to fill a substitution list from scratch.
Unfortunately qt seems to deliver only empty substitution list for any
given font.

So, how is this supposed to work ?

By the way QFont::lastResortFont crashes as it call qFatal. Strange
behaviour for an publich qt function ...