Allow use of JDK8 with older Ants.

See:

  http://stackoverflow.com/questions/23442621/ant-class-not-found-javac1-8
  https://netbeans.org/bugzilla/show_bug.cgi?id=213403
Merge pull request #116 from retronym/topic/jdk8

Allow use of JDK8 with older Ants.