wined3d: Don't free D3D swapchains until the wined3d swapchain is destroyed.

wined3d: Don't free D3D swapchains until the wined3d swapchain is destroyed.

This will allow us the get rid of the swapchain refcounting hacks in d3d9 in
particular. This is similar to the way we handle resources that are still in
use by a stateblock, but aren't referenced anywhere by the application.