The time is stored in a signed 64 bit integer with nanosecond accuracy. This eliminates the possibility of floating-point inaccuracies.
`monotonic_t` can currently hold values large enough to work correctly for more than 200 years into the future.
Using a typedef instead of directly using `int64_t` everywhere will also allow easily changing the datatype in the future should the need arise for more precise or bigger time values.
kitty didn't compile on FreeBSD for me because of unused parameters in glfw/null_joystick.c, so I added the `UNUSED` attribute to them.
I also added `UNUSED` to the unused parameters in glfw/null_monitor.c and glfw/null_window.c as well even though they are probably not used.
