[time-nuts] low power divide by 5

[ed breya]

74AC logic would do it just fine, but needs 5V nominal for full-speed 
specs. Lower supply voltage should work, but probably not all the way 
down to 3.3V with 50 MHz clocking. The spec sheets should indicate the 
possible range.

The 74AC390 can provide divide by 5 directly, with another divide 5 and 
two divide 2 sections left over - lots of capability.

Ed