Andrey Skvortsov <andrej.skvortzov@gmail.com> [Wed, 26 Sep 2018 12:13:23 +0300] rev 2344
use nice and pretty mono font in graphical languages (SFC, FBD, LD) as well
it looks like that was original idea, but some bug squashed in and
default font was used for POU.
at the same time fix use of mono font in the header of Variable panel
for SFC/FBD/LD POUs.