Use Azathoth when it comes out next week. I incorporated swap chain support a week or so ago, not using that patch though since it was far too manual to enable and propagated D3D-specific terms (like 'swap chain') to the interface which is wrong.
In Azathoth all you have to do is call createRenderWindow more than once. The D3D plugin figures out when it should be a swap chain or not internally.
As I understand it there already is if you use the GLX platform manager. The SDL platform manager can only handle one window since SDL is designed one window.