(is-mouse-button-down 0) always t, even when left mouse button is not down

is-mouse-button-up has similar problem.
is-mouse-button-pressed, and is-mouse-button-released seem to behave more like ..-down and ...-up respectively.

I was able to reproduce this on another computer, with another mouse and with clisp, and with other mouse-buttons.

I was only not able to reproduce it when compiling similar code with c, where the corresponding functions seem to act as expected.