SI-8852 Support joint compilation of Java interfaces w. statics

We had to change the java parser to accomodate this language
change in Java 8.

The enclosed test does not require JDK8 to run, it only tests
JavaParsers.

Here is a transcript of my manual testing using Java 8.

```
% tail test/files/run/8852b/{Interface.java,client.scala}
==> test/files/run/8852b/Interface.java <==
public interface Interface {
  public static int staticMethod() {
  	return 42;
  }
}

==> test/files/run/8852b/client.scala <==
object Test extends App {
  assert(Interface.staticMethod() == 42)
}

// Under separate compilation, statics in interfaces were already working
% rm /tmp/*.class 2> /dev/null; javac -d /tmp test/files/run/8852b/Interface.java && scalac-hash v2.11.2 -classpath /tmp -d /tmp test/files/run/8852b/client.scala && scala-hash v2.11.2 -classpath /tmp -nc Test

// Under joint compilation, statics in interfaces now work.
% rm /tmp/*.class 2> /dev/null; qscalac -d /tmp test/files/run/8852b/{client.scala,Interface.java} && javac -d /tmp test/files/run/8852b/Interface.java && qscala -classpath /tmp -nc Test
```
Merge pull request #3989 from retronym/ticket/8852

SI-8852 Support joint compilation of Java interfaces w. statics