This #include "../arduino.h" was the only reason prohibiting
Configtool users from storing printer and board configuration
files wherever they wanted. Good reason to remove this restriciton.
This also solves a part of issue #152.
Test code which wants to customize config.h can do so without
touching config.h itself by wrapping config.h in a macro variable
which is passed in to the compiler. It defaults to "config.h" if
no override is provided.
This change would break makefile dependency checking since the selection
of a different header file on the command line is not noticed by make
as a build-trigger. To solve this, we add a layer to the BUILDDIR path
so build products are now specific to the USER_CONFIG choice if it is
not "config.h".
Markus Hitter
Phil Hord