Have (and document) libvlc_media_get_duration return ms

in order to be consistent with other libvlc methods (libvlc_media_player_get_length, get_time, ...)

include/vlc/libvlc_media.h

@@ -263,7 +263,7 @@ VLC_PUBLIC_API libvlc_event_manager_t *
                                            libvlc_exception_t * p_e );
 
 /**
- * Get duration of media descriptor object item.
+ * Get duration (in ms) of media descriptor object item.
  *
  * \param p_md media descriptor object
  * \param p_e an initialized exception object

src/control/media.c

@@ -535,7 +535,7 @@ libvlc_media_event_manager( libvlc_media_t * p_md,
 }
 
 /**************************************************************************
- * Get duration of media object.
+ * Get duration of media object (in ms)
  **************************************************************************/
 int64_t
 libvlc_media_get_duration( libvlc_media_t * p_md,
@@ -549,7 +549,7 @@ libvlc_media_get_duration( libvlc_media_t * p_md,
         return -1;
     }
 
-    return input_item_GetDuration( p_md->p_input_item );
+    return input_item_GetDuration( p_md->p_input_item ) / 1000;
 }
 
 /**************************************************************************