[boost] [gil][io_ew] performance test

Hi there, I did a little performance test of io_new vs io2. The code is here. http://pastebin.com/eCeFZuMS On my machine io_new runs in 1.15sec for 2658 jpegs. IO2 run in 1.005sec. All jpegs are the same image but they are a different file. This way I'm sure I don't have to convert the image into a different color space. I did that since io2 doesn't support any_image, I believe. Thanks, Christian