InterruptLock: Redesign to simplify porting for different interrupt priorities.
Get rid of AtomicTempLock() and make InterruptTempLock() do what AtomicTempLock() did.
We don't need the old InterruptTempLock() semantics which didn't disable interrupts if we were in an interrupt on ARM.
It's better to do some redundant interrupt disabling than have race conditions.
PrinterMain: Fix for nested interrupts.
MotionPlanner: Fix for nested interrupts.
AxisStepper: Remove dead code.
Sam3uAdc, Sam3xAdc: Fix for nested interrupts.
At91Sam3uClock: Fix for nested interrupts.
Mk20Adc: Fix for nested interrupts.
MotionPlanner: Fix for nested interrupts.
At91Sam3uPins, At91Sam3xPins: Add some missing locking.