Do not forget to use the drift when converting stream to system clock.

It has no consequence (because of the way we actually use the clock) but
it is more consistent.

src/input/clock.c

@@ -274,7 +274,7 @@ void input_clock_ChangeRate( input_clock_t *cl, int i_rate )
     /* Move the reference point */
     if( cl->b_has_reference )
     {
-        cl->last.i_system = ClockStreamToSystem( cl, cl->last.i_stream );
+        cl->last.i_system = ClockStreamToSystem( cl, cl->last.i_stream + AvgGet( &cl->drift ) );
         cl->ref = cl->last;
     }
 
@@ -318,7 +318,7 @@ mtime_t input_clock_GetWakeup( input_clock_t *cl )
 
     /* Synchronized, we can wait */
     if( cl->b_has_reference )
-        i_wakeup = ClockStreamToSystem( cl, cl->last.i_stream );
+        i_wakeup = ClockStreamToSystem( cl, cl->last.i_stream + AvgGet( &cl->drift ) );
 
     vlc_mutex_unlock( &cl->lock );