RFR: 8035150 ShouldNotReachHere() in ConstantPool::copy_entry_to

[Staffan Larsen]

This is an attempt to solve a crash while redefining a class that has unresolved class references in its constant pool. I would appreciate some extra scrutiny here since I am unfamiliar with this code path.

I have also added a test that causes a JVM crash without the fix. 

The updates to the test library is all code copied from the jdk version of the test library.

webrev: http://cr.openjdk.java.net/~sla/8035150/webrev.00/
bug: https://bugs.openjdk.java.net/browse/JDK-8035150

Thanks,
/Staffan