Tracing idea

[Edward Z. Yang]

Excerpts from Tyson Whitehead's message of Sun Feb 20 07:14:56 -0500 2011:
> I believe a back trace on the actual call stack is generally considered not 
> that useful in a lazy language as it corresponds to the evaluation sequence,  
> That is, it is demand centric while written code is production centric

Yeah, such a buffer wouldn't be very useful for end-users; I'm thinking more
in terms of going "backwards in time" for the STG execution.

Cheers,
Edward