Mark3 RTOS Source

-Adding DCPU emulator "hello world" example
-Also, replacing all tabs with 4 spaces

Fixed a couple of bugs in the DCPU VM core
-Wrong operand used in JSR opcode, causing incorrect jumps
-Incorrect stack pointer pre/postincrement operators in push/pop

Removing the previous uart driver directory - which is causing the 644/1284p/1280 ports from working properly

Fixing the SWI code in the 1280 port.

Adding preliminary atmega1280 support... context switching should be OK

Adding automated unit testing script for running the test code on a connected Arduino board running the Mark3 bootloader

-Fixed up some documentation and functionality related to the timer-tolerance feature
-Fixed the semaphore unit test
-Adding python script used to automate the execution of unit tests under simavr

Added "tolerant" timers, allowing for improved interrupt performance (i.e. better power management due to fewer interrupts/CPU wakeups)

Updating Analog test code

Adding basic A2D test