RFR(XS): 8206022: Add test to check that the JVM accepts class files with version 56

[Mikael Vidstedt]

Please review this small change which adds a test for verifying that the JVM accepts the new (in jdk12) class file version 56:

Bug: https://bugs.openjdk.java.net/browse/JDK-8206022
Webrev: http://cr.openjdk.java.net/~mikael/webrevs/8206022/webrev.00/open/webrev/ <http://cr.openjdk.java.net/~mikael/webrevs/8206022/webrev.00/open/webrev/>

Note: I did "hg cp” from the corresponding Class55.jasm, and it seems that webrev incorrectly assumes that I *moved* the file. I’ll ensure before pushing that no files are, in fact, removed - the only change should be a single new file.

Cheers,
Mikael