Implement an ITM packet encoder?

At present, itm-decode (as the name implies) only decoded ITM packets. Eventually is may be useful to easily craft a specific trace stream, if for nothing else, an improved test bench to both this library and all that depend on it. If you want to craft a trace right now you need to to it byte-for-byte by hand.

If this is implemented, a more suitable name would be itm-protocol.