playlist: Fix playlist_Control undefined behavior

../../src/playlist/control.c:145:21: warning: passing an object that
undergoes default argument promotion to 'va_start' has undefined
behavior [-Wvarargs]
    va_start( args, locked );

include/vlc_playlist.h

@@ -302,7 +302,7 @@ VLC_API void playlist_Deactivate( playlist_t * );
  * \param b_locked TRUE if playlist is locked when entering this function
  * \param variable number of arguments
  */
-VLC_API void playlist_Control( playlist_t *p_playlist, int i_query, bool b_locked, ...  );
+VLC_API void playlist_Control( playlist_t *p_playlist, int i_query, int b_locked, ...  );
 
 static inline void playlist_ViewPlay(playlist_t *pl, playlist_item_t *node,
                                      playlist_item_t *item)

src/playlist/control.c

@@ -138,11 +138,11 @@ static void playlist_vaControl( playlist_t *p_playlist, int i_query,
     PL_UNLOCK_IF( !locked );
 }
 
-void playlist_Control( playlist_t *p_playlist, int query, bool locked, ... )
+void playlist_Control( playlist_t *p_playlist, int query, int locked, ... )
 {
     va_list args;
 
     va_start( args, locked );
-    playlist_vaControl( p_playlist, query, locked, args );
+    playlist_vaControl( p_playlist, query, (bool)locked, args );
     va_end( args );
 }