Merge remote-tracking branch 'upstream/Marlin_v1' into Marlin_v1

Conflicts:
	Marlin/Marlin.pde
	Marlin/ultralcd.cpp
	Marlin/ultralcd_implementation_hitachi_HD44780.h
Add lcd_buzz function to ultralcd.h so that non-LCD code can make use of lcd's buzzer.

Argument order of lcd_buzz was set to mirror that on tone(). Change
default M300 frequency to something audible.
Make DOGLCD merge neater.
Merge commit '1c127217df70ba25d0eb611688063c245fb2c36d' into i2c_lcd

Conflicts:
	Marlin/Marlin.pde
	Marlin/ultralcd.cpp
fix DEFAULT_AXIS_STEPS_PER_UNIT minor Z rounding error
Merge pull request #459 from martinxyz/fix-rounding-error

fix DEFAULT_AXIS_STEPS_PER_UNIT minor Z rounding error
Solved minor bug in controllerFan()

Extruder 2 was checked where extruder 1 should be checked.
Merge pull request #464 from arnoudja/Marlin_v1

Solved minor bug in controllerFan()
Merge branch 'Marlin_v1' into i2c_lcd