ErikZalm/Marlin — pull request #490 by buildrob101 (2013-05-22 11:35:56+00:00)
Title: Revert previous change pin check change

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. (From #407)