The crash was happening because add_method wasn't telling it's caller 
something went wrong.  We then ended up with a vfunc and a regular field 
on the TYPE_MEMBERS list, but only the field in the 
CLASSTYPE_MEMBER_VEC.  So we knew there was a virtual func, but couldn't 
find it.

Fixed by having add_method return false.  But that leads to the 
possibility of having NULL slots during class definition time as 
get_member_slot would always create the slot.   I should have know that 
might bite somewhere else.  So fixed by breaking get_member_slot into a 
finder and an adder.

nathan
-- 
Nathan Sidwell