[Tinyos Core WG] atm128 timer change

[Philip Levis]

I've changed the atm128 power management to no longer automatically  
consider timer0 wakeup latencies. Instead, I pushed this into the  
timer0 code as an McuPowerOverride. A simple test with a multimeter  
suggested it was working correctly. I'll try to do some better tests  
tomorrow. Now that this is in place, I'll update 112 for the WG to  
review.

Phil