Improve hzto():
Round up instead of down and then add 1 tick. This fixes sleep(1)
sometimes sleeping for < 1 second and usleep(10000) sometimes sleeping
for as little as 1 usec + syscall time.
Don't do all the calculations at splhigh().
Don't depend on `tick' being a multiple of 1000.
Don't lose accuracy for `sec' between 0x7fffffff / 1000 - 1000 and
0x7fffffff / hz.
Don't assume that longs are 32 bits or that ints have the same size as
longs.
6976af69e8