Traditionally, grdc would obtain time through time(3) which in turn gets only the second part of clock (CLOCK_SECOND), and sleep for 1 second after each screen refresh. This approach would have two problems. First, we are not guaranteed to be waken up at the beginning of a whole second, which will typically exhibit as a "lag" on second number. Second, because we sleep for whole second, and the refresh process would take some time, the error would accumulate from time to time, making the lag variable. Make grdc(6) to use time(3) to get time only at the beginning, and sample time in CLOCK_REALTIME_FAST granularity after refreshing, and use the nanosecond part to caculate how much time we want to sleep. PR: bin/120813