Makefile for Arduino command line building.

This makefile will grab all C, C++, and S files in the current directory, compile them and link them together with the Arduino libraries.
It does not compile the silly .pde files the Arduino uses by default.

See the testbench directory for a sample of how to use the makefile.
Commands to test:
make - build everything.
make clean - Un-build everything.
make upload - Write to Arduino flash memory.
make monitor - Bring up a serial monitor.
make upload_monitor - upload and monitor.

Inspect the generated assembly code by viewing build/testbench.asm

Known problems:
The makefile will use wildcards, which basically means that even if you remove a source file, the corresponding object file will be left in the build directory and included when linking. The solution is to do "make clean" whenever a source file is removed.

Unknown problems:
I have no idea of how this makefile can be used to generate libraries for use in other projects.