Between Clutter 0.8 and 1.0, the new-frame signal of ClutterTimeline
changed the second parameter to be an elapsed time in milliseconds
rather than the frame number. However a few places in clutter were
still calling the parameter 'frame_num' which is a bit
misleading. Notably the signature for the signal class closure in the
header was using the wrong name. This changes them to use 'msecs'.