RFR (S) JDK-8202758: SIGSEGV calling Class.forName(String,Boolean,ClassLoader) with mocked loader

[Lois Foltan]

Please review this change to ensure that a given ClassLoader's unnamed 
Module is a valid instance of java.lang.Module with the JVM.

open webrev at http://cr.openjdk.java.net/~lfoltan/bug_jdk8202758/webrev/
bug link at https://bugs.openjdk.java.net/browse/JDK-8202758

Testing: hs-tier1-3, jdk-tier1-3 in progress

Thanks,
Lois