- Remove DBUG calls from my_winfile.c where call and parameters
  are already printed by mysys.
- Remove DBUG from my_get_osfhandle() and my_get_open_flags() to remove
  DBUG noise.
- Updated convert-debug-for-diff to take into account windows.
- Changed some DBUG_RETURN(function()) to tmp=function(); DBUG_RETURN(tmp);
  This is needed as Visual C++ prints for DBUG binaries a trace for
  func_a()
  {
    DBUG_ENTER("func_a");
    DBUG_RETURN(func_b())
  }
  as
  >func_a
  <func_a
  >func_b
  <func_b
instead of when using gcc:
  >func_a
  | >func_b
  | <func_b
  <func_a