DERBY-6322: Remove erreoneous warning in NetBeans: superfluous use of super to access inherited member variable

This code in SortBufferScan makes NetBeans (7.4beta) issue a warning:

return (super.current != null);

"Incompatible types: boolean is not a functional interface <identifier expected>
; expected"

Patch derby-6322 removes the redundant "super." prefix.

git-svn-id: https://svn.apache.org/repos/asf/db/derby/code/trunk@1519007 13f79535-47bb-0310-9956-ffa450edef68
DERBY-6276: Convert lang/DB2IsolationLevels.sql to JUnit

Patch which performs the conversion.

git-svn-id: https://svn.apache.org/repos/asf/db/derby/code/trunk@1519008 13f79535-47bb-0310-9956-ffa450edef68