DERBY-6408: EXISTS returns NULL instead of FALSE
DERBY-6409: Wrong result from quantified comparison

Backported revisions 1573548, 1573935, 1574464 from trunk.


git-svn-id: https://svn.apache.org/repos/asf/db/derby/code/branches/10.10@1574505 13f79535-47bb-0310-9956-ffa450edef68