For OSX, use Craig's 1.0.5 build with new gcc 4.8.1

I've integrated Ardupilot changes to latest Arduino 1.0.5-r2-git, and then integrated avr-gcc 4.8.1 from the upstream Arduino 1.5.x-avr-gcc-4.8.1 branch.

avr-gcc 4.8.1 produces significantly smaller code (about 20% smaller for ardupilot-mpng), and benchmarking for other codebases shows significant (1.5x to 8x) performance speedup, with highest speedup when there's a lot of I/O.

Changes from Arduino 1.0.3 to 1.0.5-r2-git can be found in the [Arduino release notes](http://arduino.cc/en/Main/ReleaseNotes)