Fix Compiler errors when not using Oracle JDK
A few sources depend on *.sun.* classes which are available in the
Oracle JDK but not necessarily in generic Java 5, 6 or 6.
When .classpath enforced plain JavaSE 5, 6, 7, those sources would not
compile.
Merge pull request #581 from berryma4/3.3.x

Fix Compiler errors when not using Oracle JDK