FOP-2298: Java 5 doesn't support String.isEmpty

git-svn-id: https://svn.apache.org/repos/asf/xmlgraphics/fop/trunk@1523706 13f79535-47bb-0310-9956-ffa450edef68
FOP-2298: Java 5 is more strict than Java 6 about use of @Override on implementation of interface methods.

git-svn-id: https://svn.apache.org/repos/asf/xmlgraphics/fop/trunk@1523709 13f79535-47bb-0310-9956-ffa450edef68