Mark3 RTOS Source

- Added a bunch of "how-to" examples based on flAVR
- Fixed up the GUI library and built-in control code, added a GUI example (using flAVR, again)
- Ported idle-function support to all current AVR targets
- Got rid of some old examples that were more confusing than helpful
- Moved profiling and sanity tests into the unit-test directory, and refactored to support the unit-test APIs
- unit-test APIs now moved out of the "middleware libraries" section, and now get built into the UT platform directly
- Added thread-state tracking to Thread object. APIs allow a user to see if threads are ready, blocked, stopped, or exit'd.
- Fixed a bunch of instrumentation code that breaks now that g_pstNext is volatile
- Changed stacks in UT code to K_WORD from K_UCHAR (portability issues)
- Fixed logic in semaphore/mutex/event-flag objects to determine when a Yield() is required.
- Previous implementation did not handle priority inheritence properly
- Fixed bug preventing round-robin scheduling from being applied to static threads (those created before the kernel starts)
- Fixed a bug in Thread::Exit() that could hang the kernel in a variety of circumstances
- Fixed a similar bug in Thread::Stop()
- Change to remove pending timer callbacks from threads when Thread::Stop() is called, which could cause trouble.
- Fixed a bug in Timers where erratic behavior could be observed due to the m_ulTimerTolerance flag not being initialized
- Fixed a bug in Round-Robin scheduling where unblocking multiple threads in a given priority level can result in the wrong thread being scheduled.
- New approach ensures that threads get added to the *tail* of the threadlist, not the *head*

Summary:
- Dynamic threading is much more reliable (Stop & Exit behavior)
- Round-robin scheduling is much more reliable
- Timers are more reliable
- Priority inheritence works correctly
- Idle function works on all supported AVRs.