What I'm saying is that
[...]
((input-pending-p)
nil)
((<= seconds 0)
(or nodisp (redisplay)))
[...]
would become
[...]
((input-pending-p)
nil)
((<= seconds 0)
(to-be-determined-call-to-timer-check)
(or nodisp (redisplay)))
[...]
The idea is to compensate for input-pending-p no longer calling
timer_check so as sit-for will behave the same.