Implemented GraphicsDevice.Reset, Windows/DirectX only.

Does the same thing as GraphicsDeviceManager.ApplyChanges within its Windows/DirectX block.
The common situation this is used is for a tool that needs to do xna rendering on a single control and doesn't even have a game/graphicsdevicemanager.
Did you still want me to make this change? Note that the method was not previously defined for any platforms, it was inside a comment block including the other overloads.