This function is called only from three sites, it doesn't need to be in
common.h.
The implementation was already in systemdirsappend.cpp, so a matching
header was created for it.
This reduces the visibility of the function to only the files that need
it and slightly shrinks common.h.
For a start, this contains the GAL display settings (AA settings and
grid styling).
In future, other modedit-specific settings could go here too.
Fixes: lp:1672150
* https://bugs.launchpad.net/kicad/+bug/1672150
SELECTION now holds EDA_ITEMs not BOARD_ITEMs so various places had to
change to casting the selected items to BOARD_ITEMs.
Fixed compilation warnings on clang (Tom)
When creating a copy of CONTEXT_MENU, always a CONTEXT_MENU instance was
constructed, whereas an inherited type should be used. Solved with
CONTEXT_MENU::create() that has to be overridden in inheriting classes.
Event & update handlers are now virtual functions, instead of setting
the handlers with Set{Event,Update}Handler().
Wayne Stambaugh
John Beard
Jon Evans
Maciej Suminski
Miguel Angel Ajo