(I thought I had committed this already...)

On Mac, kioslave must be built as an app bundle to prevent keyboard input issues (for instance during the authentication step with kio-gdrive) but it must also be found in the expected location and, ideally, not put up a menu bar nor appear in the app switcher.

This patch achieves all that:

• installs a wrapper script that proxies the kioslave app bundle-exec
• adds the CoreFoundation magic code that instructs the application to behave as an agent.

Works as intended with all kioslaves I tested.

Alternatively one could use a Mac-specific hard-codec path to launch the bundle-exec instead of installing the wrapper script. That would require patching klauncher - and I don't know if this the only place where kioslave is started.