Clean up KReportUnit
- remove KReportUnit::ListOption (T4967), add Invalid type, better support descriptions and symbols
- mark default constants as extern to avoid copying, add DEFAULT_UNIT_TYPE
Build KReport with tests enabled, run tests, run KReportExample, try the Unit combo for the page units.
Build Kexi with this KReport - no changes needed.
(switching units for page is still broken but this is not related to this very patch)
Reviewed By: piggz
Maniphest Tasks: T4967
Differential Revision: https://phabricator.kde.org/D6756