- port to categorized logging using the macros provided by ECM,
  and export a category file for kdebugsettings;
- bump the version of ECM, and then the version of Frameworks,
  to the minimum version where the macros are included;
- remove KDE_NO_DEBUG_OUTPUT, previously used by kDebug and
  superseded like kDebug by Qt categorized logging;
- cleanup of the level of (very) few log messages; in general,
  all the existing log calls should be rechecked, and either
  removed or cleaned;
- reword two poorly worded messages.