Use module path instead of class path for stdlib on Java 9

Also report the "named does not read unnamed" error, which was not
possible previously because we wouldn't be able to read anything from
kotlin-stdlib (because it was added to the unnamed module by default)

compiler/testData/javaModules/dependencyOnStdlib/namedWithoutExplicitDependency/module-info.java

@@ -0,0 +1,2 @@
+module namedWithoutExplicitDependency {
+}