An optimized JPEG library for Arduino

I've shared this code with a few people who have contributed useful suggestions that I've implemented. I think it's ready to be called 1.0. I was toying with the idea of adding "auto-rotate" code, but it will add a lot of bulk to the project that most people will not need. The Exif orientation is available through the API if you would like to re-orient the image at the output stage.