Another random failure on build.kde.org (see T6546). This tries to use
QTRY_COMPARE on the SignalSpy's count instead of a wait in the hope that
this can handle the multi-threaded situation better. Though it might
also be possible that the other thread just didn't run in the 5 sec we
waited.
A new test class for KWinBindings added which is intended to group the
testing of the various slots set up in kwinbindings.cpp. As the scripts
also delegate to the slots this is also tested.
