Merge pull request #1 from ErikZalm/Marlin_v1

merge
Implementation of FW extruder change retract

FW retraction is extended onto swap retraction invoked by 'G10 S1'.
Bookkeeping of the retract state of all extruders allows for having one
extruder fw standard retracted while another extruder is swap retracted.
An LCD menu item for the swap retract and recover length was added.
restore Branch from Backup

sorry for that
fixed wrong compiler-option
Fix lcd itostr3() to handle negative numbers
optimised some math-code
Update pins.h

Leapfrog board added to the pin list
Update Configuration.h

Leapfrog added to the board list
Add leapfrog and dual Y/Z

I have added the pin set for the leapfrog and the support of dual Y and Z
Update temperature.cpp

Enables both SD card and MAX6675 to talk with each other
Fixes also issue #750
Update pins.h
Fix for FWRETRACT on DELTA printers.

Fixes #817
Merge pull request #2 from ErikZalm/Marlin_v1

Update my github
If the option DISABLE_INACTIVE_EXTRUDER ist active the extruder switch to early to inactive because there are some moves in the buffer. So the planner wait 32 moves to disable the unused extruder.
Fixed stop print LCD function on M104
Inverted state logic for forced_heating_stop variable
Changed the type of variable to bool, the name to "cancel_heatup", flags implementation and added this fix to M190 gcode too.
Add "Thermal Runaway Protection" feature

This is a feature to protect your printer from burn up in flames if it
has a thermistor coming off place (this happened to a friend of mine
recently and motivated me writing this feature).

The issue: If a thermistor come off, it will read a lower temperature
than actual. The system will turn the heater on forever, burning up the
filament and anything
else around.

After the temperature reaches the target for the first time, this
feature will start measuring for how long the current temperature stays
below the target minus _HYSTERESIS (set_temperature -
THERMAL_RUNAWAY_PROTECTION_HYSTERESIS).

If it stays longer than _PERIOD, it means the thermistor temperature
cannot catch up with the target, so something *may be* wrong. Then, to
be on the safe side, the system will he halt.

Bear in mind the count down will just start AFTER the first time the
thermistor temperature is over the target, so you will have no problem
if your extruder heater takes 2 minutes to hit the target on heating.
Changed the declaration of the variable to Marlin_main.cpp to fix issue on commit #965
Merge pull request #948 from Dim3nsioneer/Marlin_v1

Implementation of FW extruder change retract