This introduces the following new comparison keys in

TestCase.assertQueries():

limit - The value for a SQL LIMIT
offset - The value for a SQL OFFSET
select_for_update - Whether model.select_for_update(...) was used
values_select - Any fields passed to .values() or .value_list()

It also does a few other things to fix and aid in comparisons.
Any values in extra are now normalized. Whitespace is collapsed and

stripped. Unit tests no longer have to be aware of the exact formatting

of the SQL, which helps for more complex statements.
Queries that are generated but not executed (any that would raise a

EmptyResultSet) are now skipped for comparison. An example would be a

query on pk__in=[], which Django knows makes no sense to pass to the

database. This is a way that code can short-circuit and optimize out an

entire query or a particular clause of the query in Django.

assertQueries() now ignores it just as Django does.

Made use of these in other unit tests.