block until the lock windows are shown; prevents sleeping before locking

accomplished by:

* synchronously calling desktopResized in the screen locker app
    (this causes the locker windows to be created)
* writing to stdout, and listening for readyRead on the ksmserver side

this should probably go into the stable branch as well, but realy needs
broad testing first given that it touches ksmserver, security, sleep, etc.

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