* hotkeys: never _never_ use  demux_Control outside of src/input/ (it's
 completely broken,  there is a lot  more things to do),  all interfaces
 have  to  use  var_Get/Set  (time(-offset),  position(-offset),  state,
 rate(-slower|-faster)...  ).
 Btw,   input_SetStatus,   input_Seek,   input_Tell,   input_ChangeArea,
 input_ToggleES,  will   be  quickly   obsolete  and   removed(at  least
 unavailable for intf), so we should convert remaining interfaces (ie all
 except wx, osx, rc, http, hotkeys).

 * avi: implemented DEMUX_SET_TIME (not yet used).