shout: Flag unused param.

modules/access_output/shout.c

@@ -560,6 +560,7 @@ static ssize_t Write( sout_access_out_t *p_access, block_t *p_buffer )
  *****************************************************************************/
 static int Seek( sout_access_out_t *p_access, off_t i_pos )
 {
+    VLC_UNUSED(i_pos);
     msg_Err( p_access, "cannot seek on shout" );
     return VLC_EGENERIC;
 }