Enable build with JDK 11.0.4

[Dieter Tremel]

After switch to Oracle JDK 11.0.4 the unit tests of an application depending on jaudiotagger 2.2.3 did not work. So I tried to build with java 11 on Windows 7 x64. Some changed in pom and some modifications in test suite were necessary to build successfully. Just to inform you I attach the diff.

[IJabz]

I now have same requirement as you to be able to build with Java 11. I have made changes (but not quite the same as your diff) so now works with Java 11 and continues to work with Java 8.