WIP serde

[tatref]

Hi,

Here is the work in progress to port the full emulator from rustc_serialize to serde. It is still very rough on the edges!
I had to duplicate the "big array" trick for the Box<[T; XXX]> type. I'm not sure if there is a cleaner and more general solution.

This does not compile yet, what I did is mostly search and replace.

Don't be in a hurry to check this ;-)

Remaining:

cdrom::AsyncResponse
gpu::Callback
gpu::Gp0Handler
mdec::CommandHandler