With all the 2D refactorings thhe softsurface won't work anymore.
This also revealed a bug with the fullscreen variable, a few places were still using the old one from the SDL backend.
- disabled the mouse movement sensitivity CVARs pending a refactoring of the code to handle them in the input backend instead of the individual input handlers.
- draw fullscreen blends below the console.
- moved all mouse event processing out of the SDL backend to D_PostEvent.
- removed all remaining code for dealing with mouse buttons directly.
This removes all unused parts of the implementation and moves the rest to the InputState class for easier replacement later. All MACT is doing now here is to call the UpdateStatus function, the internal workings are no longer relevant.
