A+

wined3d: Add a WARN to IWineD3DDeviceImpl_SetFrontBackBuffers() about potentially being called without a GL context.

This can happen if the window is destroyed before the device is released.

If the replacement pipeline is used, ARBfp is always on. Disabling it
can break shaders or the replacement pipeline, because the shader and
ffp code assumes the extension is on.

There is no need to copy the frontbuffer to the screen when the backbuffer was
modified...