Merge pull request #166 from zittix/Marlin_v1

Fixes #153 for bad call to abs()
Merge pull request #164 from guanix/Marlin_v1

Melzi support
Merge branch 'Marlin_v1' of github.com:ErikZalm/Marlin into Marlin_v1
Merge pull request #159 from MaikStohn/Marlin_v1

Marlin v1 - BUG FIXES / CORRECTIONS
Limit PID autotune PWM to PID_MAX
Update Marlin/Configuration.h
Update Marlin/thermistortables.h
Update Marlin/Configuration.h
Grammar correction.
Merge branch 'Marlin_v1' of https://github.com/ErikZalm/Marlin into Marlin_v1
Add M401 - Wait for user on LCD button press
Do not initialize in the header file.
Update after testing
Last M401 update, refresh the LCD during an M401 wait.
Add strigification for extruder amount in M115 report.
Extended range above 250C. (Operating range states up to 300C)
Tested May 19 - It works! Verified with separate thermocouple TM-902C also.
Update Marlin/Configuration.h
Update Marlin/thermistortables.h
Update Marlin/thermistortables.h