Debug: traverse coroutine resume chain

[Egil Hjelmeland <privat@...>]

I don't think the debug module makes it is possible to traverse from the 
running coroutine back to the main coroutine.
Or am I missing something?
I think it will be quite useful for debugging, to list the coroutine in 
the resume chain, and inspect their stacks.
Something like debug.getresumer(co) -> co


Best regards
Egil Hjelmeland