[Reviewer: Mike][From: Alex] Copy variable parameters into internal memory

Hi Mike,

I've made a change to copy variable length parameters into memory owned by the event/marker to fix #23. Please could you review (or let me know if you don't have time). 

Note I went round the houses a bit on this one, and ended up bashing out a quick UT framework. It's probably not required given that the change ended up being quite small, but I think its worth checking in now that I've written it. 

Alex.