Also set a title in the qt examples like it is now done in the gtk example.
Fix the newly added find_video_sink in the gtk example and add similar function
to the qt examples.
Try to find a working videosink, don't hardcode xvimagesink. Also
add some borders to window and give it a title so that it's clear
that this is really a Gtk+ window and not a window created by the
videosink.
Add simple videotestsrc ! xvimagesink examples using gtk and qt. This patch also
adds all boilerplate to configure for using c++. The qt based examples are
optional like their gtk counterparts.
