Simplified stepper inactive time

Updated SERIAL define to MYSERIAL, because Arduino 1.0 defines SERIAL as 0.

if (millimeters_of_travel == 0.0) => if (millimeters_of_travel < 0.001)
(thanks mooselake)

One for common settings.
One for advanced settings.

Default off.

Needs some work to remove the blocking in read max6675.

Added late z enable. (blddk request)
Only calculate look ahead if >2 moves in buffer.
Removed some FORCE_INLINE to save memory.

Signed-off-by: Erik van der Zalm <erik@vdzalm.eu>

M109 EOL fix when TEMP_RESIDENCY_TIME is undefined; printer interface (p...

more work on Makefile - actually rebuilds if Makefile or Configuration.h are altered, also much cleaner output

M109 EOL fix when TEMP_RESIDENCY_TIME is undefined; printer interface (pronterface) could not see target extruder heater temperature to continue print

added suicide pin for a power supply to the arduino that is only active if the arduino is holding high for an output.