a) Because it's a cool piece of documentation
b) It's a real world example of using images in the documentation.
It's not turned on in the upper level Makefile yet, as I expect the
specifics of the toolchain to change over the next week or so as people
play around with this, and I don't want to the doc build mirrors to have
to suddenly update the ports they have installed. Once this has stabilised
it can be turned on.
