Rockbox

Attached patch makes plugins build and load on Clip.

I used the unmodified c200 keymap when possible.
I replaced the REC key of c200 with HOME key of Clip when needed.

I used archos graphics when possible.

Problems are:
* pegbox shows corrupted graphics but not in the simulator.
* chessbox loader is disabled, I’m not sure how to do that correctly, the comment mentions it’s needed on archos, but use if (MEMORYSIZE ⇐ 8)
* greylib doesn’t work
* I had to use a 512kB buffer for codecs to allow 512kB buffer for the plugins (not sure if it’s a real problem though)

Comments on how to fix these are welcome, I would like to commit when the 2 first problems are fixed (work on greylib can wait, and we don’t need codecs at the moment).