RFR(M): 8165896: Use "open" flag from JVM_DefineModule to export all module packages

[Rachel Protacio]

Hello!

Please review this enhancement, which implements the VM side of open 
modules. Open modules export all their packages unqualifiedly, which was 
previously done by exporting the packages one by one on the java side. 
This change saves that step by adding an internal "open" representation 
for the module structure, which is checked before checking the 
exportedness of the package itself.

JDK link: https://bugs.openjdk.java.net/browse/JDK-8165896

hotspot webrev: http://cr.openjdk.java.net/~rprotacio/8165896.hotspot.00/
jdk webrev: http://cr.openjdk.java.net/~rprotacio/8165896.jdk.00/
root repo patch:

--- old/test/lib/sun/hotspot/WhiteBox.java	2017-03-23 12:50:36.869963040 -0400
+++ new/test/lib/sun/hotspot/WhiteBox.java	2017-03-23 12:50:36.421963021 -0400
@@ -1,5 +1,5 @@
  /*
- * Copyright (c) 2012, 2016, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2012, 2017, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
@@ -449,8 +449,8 @@
    }
  
    // Jigsaw
-  public native void DefineModule(Object module, String version, String location,
-                                  Object[] packages);
+  public native void DefineModule(Object module, boolean is_open, String version,
+                                  String location, Object[] packages);
    public native void AddModuleExports(Object from_module, String pkg, Object to_module);
    public native void AddReadsModule(Object from_module, Object source_module);
    public native void AddModulePackage(Object module, String pkg);


Testing:

  * includes new regression test
  * JPRT and RBT hotspot tiers 2-5

Notes:

  * This changeset re-conceptualizes the unnamed module as an open
    module (as far as the internal representation is concerned). This
    saves the VM from specifying every package in the unnamed module as
    unqualifiedly exported.
  * Additionally, automatic modules are defined as open modules in terms
    of package exports. As such, in the jdk repo's Module.java code,
    defineModule0() is called with isOpen==true for automatic modules.
  * In my search through module startup code, I found a for-loop in
    modules.cpp that was looping through java.base packages just for
    some logging. The entire loop should have been bounded by a
    log_is_enabled() conditional. Since this patch is generally
    improving the efficiency of modules startup, I corrected that here.
  * Fixed a few comment typos I found along the way.

Thank you!
Rachel