The 'RTC' example shows the usage of the RTC and it's alarms.

Functionality:
 - The RTC is enabled and the sub-second alarm set to trigger every 250 ms.
 - The LED (DS1) is toggled each time the sub-second alarm triggers.
 - The time-of-day alarm is set to 5 seconds.
    - When the time-of-day alarm triggers, the rate of the sub-second alarm
      is switched to 500 ms.
    - The time-of-day alarm is then rearmed for another 5 sec.
 - Pressing S1 outputs the current value of the RTC via stdout using the
   console UART.

Jumper Configuration:
  No jumper configuration is required for the RTC program.
