Qt'fy access to pimpl objects: use macros Q_DECLARE_PRIVATE & Q_D
Summary:
- enforces constness some more (see issue spotted with GeoDataTrack::extendedData())
- delivers inline-ness of the access methods
- code should be more familiar to Qt developers
Reviewers: Marble, nienhueser
Reviewed By: Marble, nienhueser
Subscribers: nienhueser
Differential Revision: https://phabricator.kde.org/D2951