This simplifies code sharing between ArduCopter and Arduplane at the expense of 48bytes.
Moved CH_x defines out of the defines.h file and into the library where they belong
This reverts commit a65a2dda2c1bfa95437880227a3abddc95b329f5.
I am reverting this not for any sane reason, but because my 3 APM
boards now lock up on any I2C operation, and I don't know why. I can't
see how this change could have caused it, but I don't want to take the
chance.