This diff introduces purely cosmetic changes.

1. KCM now compiled with no signals/slot keywords to avoid clash with gtk
2. Remove linking of XCursors library, because it is no longer needed
3. Replace some for-cycles with range-based ones
4. Wrap some string literals with QStringLiteral
5. Rearrange include headers
6. Some other changes to better match code style

Check, if there is no regressions