DERBY-4403: Disallow subqueries in the GROUP BY list

backporting change #1575226 from trunk to 10.10 branch.  merged clean.

Queries that were grouped by subqueries used to fail with a
NullPointerException or an assert failure. Make them fail with a
proper syntax error instead.



git-svn-id: https://svn.apache.org/repos/asf/db/derby/code/branches/10.10@1627645 13f79535-47bb-0310-9956-ffa450edef68