Numerous modifications to decouple the RTC wiring implementation from the rest of the code and isolate it in it's own file.  Along the way, the following modifications/additions were made:
	* Full support for RTC32 (32-bit, battery backed RTC), with helper functions for saving/restoring current time on powerup
	* Fewer interrupts: for both RTC/RTC32, the counters now keep track of time without interrupts every milliseconds--RTC counters are only queried when needed
	* Callback system: functions that allow tying into the RTC and getting a callback every N seconds, working for both implementations

For legacy code, the changes are transparent.  Newer code, especially that wishing to leverage the callback system, would likely benefit from the new RealTimeClock system library (included in next commit, gimme a few seconds...).

Pat Deegan, http://flyingcarsandstuff.com
The RealTimeClock library leverages the on-board RTC available on the XMEGA, and provides services like allowing you to
	* set and query the time
	* set a periodic callback, to be triggered every N seconds

Along with modifications to the Xmegaduino library's wiring implementation, this will allow you to easily deal with an
RTC-based time system.  Use this library to get and set the real datetime, and use millis()/micros() as usual.

Assumptions:
	1) You are on a platform that has either an RTC or RTC32 support

	2) You are using a variant that actually enables the RTC
		(defines USE_RTC in the pins_arduino.h)

	3) You are using an Xmegaduino (or other Arduino compatible
		sdk) that has implemented my mods for the RTC wiring
		functionality (e.g. from https://github.com/psychogenic/Xmegaduino
		or from Xmegaduino main trunk, if the pull request has been merged).

Documentation is available within the source, on http://flyingcarsandstuff.com/projects/RealTimeClock and in the sample code included in the examples directory.

Pat Deegan, http://flyingcarsandstuff.com
Added the wasResetAtPowerup() method to RealTimeClock::Device, which allows you to know if we had a VBAT brown-out/powerloss/problem on battery-backed RTC32 systems.