DDraw: Add a few missing WINAPIs

[Henri Verbeet]

2009/9/12 Stefan Dösinger <stefan at codeweavers.com>:
> I wonder how this worked in the past, and why the compiler didn't complain.

It's pretty simple really, these functions don't need WINAPI because
they're ddraw internal functions "cleverly" disguised as vtable
methods. IIRC it's actually harmful to add WINAPI to these on OS X due
to some obscure compiler bug.