Protect LPGUID typedef by __LPGUID_DEFINED__ being defined.

Protect LPCLSID and LPFMTID typedefs, IsEqualGUID, IsEqualIID,
IsEqualCLSID, IID_NULL, CLSID_NULL and FMTID_NULL defines by
__IID_DEFINED__ being defined.

PSWIZB_DISABLEDFINISH, followed by another one without those flags
should show the next button again and hide the finish button.

In DX8 the D3DSURFACE_DESC structure has a size field which needs to be set.