KTextEditor has a hard dependency on KAuth - ensure it is available.

On Linux/FreeBSD this is normally received via KIO - however it only requires KAuth on those two platforms meaning the build will fail on Windows without this explicit dependency.

Given that KAuth is a no-op on Windows it would be worthwhile investigating if KTextEditor can have an optional dependency on KAuth as well.

CCMAIL: kde-frameworks-devel@kde.org