Vout recycling as keeping the same "vout display" plugin and not
disabling/enabling the window.

Add input_resource_StopFreeVout: Used to stop the re-used vout if there is no
video following the current input.

The vout is now always closed or paused from input_resource_PutVout(). Only the
main vout is paused, all additional vouts will be closed. The main vout will be
actually closed from input_resource_StopFreeVout(), when we are sure that the
next input doesn't have video.