http://cr.openjdk.java.net/~mchung/jdk9/webrevs/8177844/webrev.01/
This fixes -—patch-module to do hash checking on the module being patched so that it will ensure that a non-upgradeable module remains not upgradeable. As Graal has been using —-patch-module option to disable the hash checking to load a different version of jdk.internal.vm.compiler, it needs a mechanism to load Graal, as tracked by JDK-8177845. Mandy
