Make regression tests less dependent on hash table order.

Make regression tests less dependent on hash table order.

Upcoming changes to the hash table code used, among others, for grouping
and set operations will change the output order for a few queries. To
make it less likely that actual bugs are hidden between regression test
ordering changes, and to make the tests robust against platform
dependant ordering, add ORDER BYs guaranteeing the output order.

As it's possible that some of the changes expose platform dependant
ordering, push this earlier, to let the buildfarm shake out potentially
unstable results.

Discussion: <20160727004333.r3e2k2y6fvk2ntup@alap3.anarazel.de>