cl-sdl only returns events for mouse buttons 1-3.
I used the following hack to return the actual button state instead of
intercepting and filtering it, so I can support the scroll wheel in my program (buttons 4-5).
Please implement more buttons cleanly in the wrapper so I do not have to resort to modifying cl-sdl.
Perhaps return the button state as I have done, and provide macros to logior to determine individual button states?