d3d: avoid implicit conversion warnings from identical enumeration types D3DPOOL and WINED3DPOOL (Clang)

[Henri Verbeet]

2011/5/16 Frédéric Delanoy <frederic.delanoy at gmail.com>:
> Is there in that case no point in getting rid of those warnings by
> adding conversion functions between those related-but-not-identical
> enums?
>
Well, in case of something like IDirect3DCubeTexture9Impl_GetType()
there's no point in asking wined3d at all, the implementation should
just be "return D3DRTYPE_CUBETEXTURE;". In case of something like
IDirect3D9Impl_CheckDeviceFormat() we should have a conversion
function.