[Reviewer Andy] Dynamic Sproutlet loading

Andy

Can you review the changes for dynamic sproutlet loading.  I'll email updated spec separately.

Mike
Yes - I was going round in circles because some of the GCC docs on the subject are out of date, and converting numeric #defines to C strings was really fiddly given the constraints, so I decided life was too short.  I was going to discuss in planning whether we think we need a follow-on story to do more firewalling here.