Soft PWM. (Sanguinololu can also have PID temperature control)
Interrupt save WRITE for addresses > 0x0FF

heating up santity, formarly knows as "watchdog", but renamed due to the existance of the real watchdog, works now.

Fix M201 not saving settings in all places, so the changes did not get written into EEPROM

added a partial release option to "m84" aka "stepper release". If you do tiny layers, you might want to keep the z-axis powered to not loose height positioning after homeing.

fixed the st_synchronize. it would have continued if there is only the last move of the buffer being stepped.

- The temperature control is pretty much complete
  (not sure what to do w/ autotemp though)
  Changed the pins assignment to clearly separate bed and extruder heaters
  and temp sensors, changed a bit how termistor tables are handled.
- The steppers control is rudimentary
  (only chanages what pins it uses depending on the active_extruder var,
   but that's enough for switching extruder in the start.gcode in the
   the profiles)
- Tested only w/ RAMPS 1.4

added M503 to display eeprom storage, and renamed eeprom routings. This version is compatible with the qtmarlin eeprom-tab.

Found a couple of unused variables, that I commented.
Tried to solve the program memory warning message, and failed.

Advance (not tested)

Might be replaced by something more clever, e.g. by erik, and does not yet support the second extruder or the bed.
its kind of not so cool, because you need 6 more ints.
Maybe isheating() should use the degrees directly, as it is not used in time-critical anyways.
Then it would be much easier. to have the offsets without additional variables.