Migrate the filling of the line buffer into a seperate function.
This does naturally reduce the cost of the loop management but
much more importantly allows us to use viper native code
generator.
At this point both the simulator and a PineTime will come up
and show a clock (although in the case of the PineTime the clock
will just come up at 12:00).
Currently this supports time only (no date) and it based on the
RTCounter class which is customized for nRF ports. At present
the nRF port doesn't have proper machine.rtc support so we have
implemented within wasp instead.
