Optimize images with lossless compression

I use ImageOptim to compress images for all 6.x and 7.x branches. Here are the patches.

It was saved about 5kB for 7.x-3.x branch to give a example. Not much, but as deekayen said at the core issue:

The goal here is not really performance as catch tagged it. We're really only talking about a couple of bytes per image. It's not hugely significant there.

My reason for going through this issue is because every time someone runs YSlow or Google Page Speed to optimize their site, they're going to get notified that their site could be faster if they had used compressed or optimized images, then it will list these images and their compressed options.