Run avr-size with the --mcu=... -C option as well.  That reports how
much actual device program and data memory is used along with a
percentage fullness.

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

Often it can be useful to see the actual commands being run by make.
Other projects (eg, the Linux kernel) support this with a "V=1" make
parameter.  Do the same here.

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

+ Removed most explicit pathnames, use the standard make "VPATH" to let
make find the files for itself.

+ Added a "hardware variant" variable that allows compiging Sanguino and
Gen7 as well as "generic" arduino.

+ Allows overriding the MOTHERBOARD define from the Makefile

+ Removed the 'preprocessor' bit that wasn't needed, now just "include" the
files that are needed, since it allows gcc to show the right file/line
when displaying error/warnings.

+ Uses gcc's own dependency generator to generate the .d files, and
and include these instead of self-patching the makefile

Signed-off-by: Michel Pollet <buserror@gmail.com>

This adds flexibility to the makefile by allowing different pde
targets to be specified for different needs.