- adjustment to the previous checkin regarding inheritance to not conflict with globals

- adjustment to the previous checkin regarding inheritance to not conflict with globals
- fix to self-referential eager loading such that if the same mapped
instance appears in two or more distinct sets of columns in the same
result set, its eagerly loaded collection will be populated regardless
of whether or not all of the rows contain a set of "eager" columns for
that collection.  this would also show up as a KeyError when fetching
results with join_depth turned on.