LUCENE-5207: Revert the dynamic class name. Its much better to use the "source file attribute". The class name is now constant (as every class gets own class loader) and looks like an internal class of the compiler. The stack trace is then looking like:
Throwable #1: java.lang.IllegalArgumentException: foobar
       at __randomizedtesting.SeedInfo.seed([3968E8DD2901F71C:4292B9595A397818]:0)
       at org.apache.lucene.util.MathUtil.log(MathUtil.java:51)
       at org.apache.lucene.expressions.js.JavascriptCompiler$CompiledExpression.evaluate(logn(2, 0))
       at org.apache.lucene.expressions.js.TestJavascriptFunction.assertEvaluatesTo(TestJavascriptFunction.java:27)
       at org.apache.lucene.expressions.js.TestJavascriptFunction.testLognMethod(TestJavascriptFunction.java:178)
       at java.lang.Thread.run(Thread.java:724)

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/lucene5207@1522907 13f79535-47bb-0310-9956-ffa450edef68