fix loop timing and colon tick glitch
fix loop timing and colon tick glitch

fixes issue reported by hachi in #10 but in a different way due to code size concern for smaller mcus

( unfortunately this approach expects an arbitrary loop delay (1/8 sec)that doesnt perfectly align to seconds.
 I suspect we can fix that later by managing a more reliable timer based ticker in the future).

zerog2k/stc_diyclock,zerog2k/stc_diyclock,zerog2k/stc_diyclock