Put the DirectX9 stuff into a namespace.

This makes it almost build on Windows, but not quite.  Some required files excluded from build, still.

With this, there are only a few errors left, and they're mostly from GPU/Directx9/helper/fbo.cpp.  I couldn't find information on the types used... missing are D3DVECTOR4, pD3Ddevice->Resolve, d3dpp.FrontBufferFormat, D3DFMT_LE_A8R8G8B8, pD3Ddevice->SetRingBufferParameters, and D3DRING_BUFFER_PARAMETERS.

-[Unknown]