DERBY-5840: Clean up compiler warnings introduced by using Java 5 language features

Tell JavaCC to generate Java 5 code for the parsers. This change
silences the warnings previously seen when compiling the parsers, so
it also removes the build target that post-processes the parsers and
inserts @SuppressWarnings annotations.

git-svn-id: https://svn.apache.org/repos/asf/db/derby/code/trunk@1486039 13f79535-47bb-0310-9956-ffa450edef68