VP1Utils+VP1GeometrySystems: slots -> Q_SLOTS
Rename the Qt slots 'keyword' to Q_SLOTS.
Having this in the source confuses cppcheck, which reports syntax errors. We can define slots as a macro expanding to nothing in the cppcheck configuration, but if we do that globally, there are other packages that break because they use slots as an identifier. Using Q_SLOTS instead prevents this name collision.