gtk: Block value-change signal handler while updating the range of the seekbar too
gtk: Block value-change signal handler while updating the range of the seekbar too

I.e. when updating the duration. Changing the range might also change the
value, which would then trigger a seek.

sdroege/gst-player,sdroege/gst-player,sdroege/gst-player,sdroege/gst-player,sdroege/gst-player