Add M401 - Wait for user to press button on LCD (with optional timeout) minor fix in M115.

Marlin v1 - BUG FIXES / CORRECTIONS

Melzi support

Fixes #153 for bad call to abs()

Marlin v1 ultimaker rc3

Turning off the protection might be beneficial to those who want to do fast and long reversals.

This reverts commit 3682d9bd5b.

This is required when moving the buttons_init() function to the
lcd_init() function

Since the class "MainMenu" was used within a static variable the
initialization of the object (constructor call) was done before Arduino
library startup. It always caused a crash when using AVRStudio with
JTAG debugger (caused from calling the LCD initialization / the lot of
I/O work / the stack used during this calls). By moving the LCD_INIT
out of the constructor and using an explicit call inside of Arduino
setup() implementation immediately fixed all problems and the JTAG
debugger runs fine.