- Added "Z_RAISE_BEFORE_HOMING" for raising Z the defined distance
before homing. This is useful to avoid Z-Probe collision when hotend is
near bed.

- Fixed the issue of Z not going bellow Z_PROBE_OFFSET when
"min_software_endstops" is true.
Now the Z_PROBE_OFFSET is not set in Z_MIN_POS, it is added after
homing.

If "SHOW_TEMP_ADC_VALUES" is defined in Configuration_adv.h, the M105
command will present, after tradicional temperatures, the ADC value read
from temp sensors. This is great for adjusting thermistor tables with
thermocouple.

From Pronterface you can see the ADC value and compare with a
thermocouple reading.. then you just need to create your own thermistor
table.

Since this merge doesnt change the original information, it doesnt mess
with PC software parsing (tested under Pronterface and Repetier-Host).

Check the Readme for instruction how to enable and configure the feature

As well a couple of minor changes to handling of extruder offset for
dual x-carriage mode.

Also added a couple of missed merge lines in homeaxis() from previous
commit.

add more delta defaults
on delta make second home even slower

Dual x-carriage designs offer some substantial improvements for dual
extruder printing.

Untested

M109 S180 waits only when heating.
M109 R180 also waits when cooling.

Diffed and merged, preserving my updates

Integrated fixes from henrikbrixandersen pull request #504

Reviert previous change of #if BLAH_PIN > 0 to #if defined(BLAH_PIN) &&
BLAH_PIN > -1. Unfortunately some times pin 0 is used. For my sins I've
gone through and replaced all unsafe checks of #if BLAH_PIN > -1 with
the safe version.

The for loop for Axis count over the Array.
Add a break after M907

Extruder 2 was checked where extruder 1 should be checked.

If S is left out perhaps it should be silent, but check the spec for
this M code.

Also refactor extruder auto fan logic to simplify further and now only
check every 2.5 seconds

Argument order of lcd_buzz was set to mirror that on tone(). Change
default M300 frequency to something audible.

Add new 'callback' edit-menu types that call a function after the edit is done. Use this to display and edit Ki and Kd correctly (removing the scaling first and reapplying it after). Also use it to reset maximum stepwise acceleration rates, after updating mm/s^2 rates via menus. (Previously, changes did nothing to affect planner unless saved back to EEPROM, and the machine reset).

Add calls to updatePID() so that PID loop uses updated values whether set by gcode (it already did this), or by restoring defaults, or loading from EEPROM (it didn't do those last two). Similarly, update the maximum step/s^2 accel rates when the mm/s^2 values are changed - whether by menu edits, restore defaults, or EEPROM read.

Refactor the acceleration rate update logic, and the PID scaling logic, into new functions that can be called from wherever, including the callbacks.

Add menu items to allow the z jerk and e jerk to be viewed/edited in the Control->Motion menu, as per xy jerk.

Conflicts:
	Marlin/language.h

The LARGE_FLASH flag allows superfluous features to be excluded
on boards with less memory