the new property is appended at the end of the existing enums such that
binary compatibility is kept. The special values at the end of the enums
are currently only used by automatic tests of KFileMetaData. There
should be no harm by this commit.
At time of this commit, lxr.kde.org shows no user of the special values
at the end of the enum. My patch should not cause any problems.
One interesting question is how to manage caching of new properties in
Baloo when one modify KFileMetaData. I currently have no idea.
There should be more patches to add new properties after this review if needed (some music related properties are still missing).