Module return codes

[Phil Mayers]

Where did we get with this? At the moment, I can't proceed with a 
migration to 3.x in the absence of last return code, and I don't want to 
use my local patch if it's not going upstream.

It doesn't look easy to do this with an xlat; the "last" return code 
only exists as local variable(s) in modcall_* functions, so we'd need to 
grow the request object to store it. Even the highest-prio code only 
exists on the relevant modcall_stack_entry_t struct, and an xlat has no 
easy way to know the position in the modcall stack/tree.

I would appreciate a steer; we have serious problems with load spikes 
and time spent on this in 2.x is wasted IMO, so I need to get onto 3.x 
and then tackle the problem.