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

Fix unchecked warnings in test packages:

  - engine
  - i18n
  - store
  - tools

git-svn-id: https://svn.apache.org/repos/asf/db/derby/code/trunk@1482862 13f79535-47bb-0310-9956-ffa450edef68