- query.from_self(), query.union(), others which do a

- query.from_self(), query.union(), others which do a
"SELECT * from (SELECT...)" type of nesting will do
a better job translating column expressions within the subquery
to the columns clause of the outer query.  This is
potentially backwards incompatible with 0.5, in that this
may break queries with literal expressions that do not have labels
applied (i.e. literal('foo'), etc.)
[ticket:1568]