Make jdk.internal.reflect package being loaded by the standard classloader (#73)

It avoids error like

Caused by: java.lang.IllegalAccessError: class jdk.internal.reflect.ConstructorAccessorImpl loaded by com/google/gwtmockito/GwtMockitoTestRunner$GwtMockitoClassLoader cannot access jdk/internal/reflect superclass jdk.internal.reflect.MagicAccessorImpl
        at java.base/java.lang.ClassLoader.defineClass1(Native Method)
        at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1007)
        at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:868)
        at javassist.Loader.findClass(Loader.java:377)
        at com.google.gwtmockito.GwtMockitoTestRunner$GwtMockitoClassLoader.findClass(GwtMockitoTestRunner.java:421)

Author: benoitf

gwtmockito/src/main/java/com/google/gwtmockito/GwtMockitoTestRunner.java

@@ -259,6 +259,7 @@ protected Collection<Class<?>> getClassesToStub() {
   protected Collection<String> getPackagesToLoadViaStandardClassloader() {
     Collection<String> packages = new LinkedList<String>();
     packages.add("com.vladium"); // To support EMMA code coverage tools
+    packages.add("jdk.internal.reflect"); // Java9 loading mechanism
     packages.add("net.sourceforge.cobertura"); // To support Cobertura code coverage tools
     packages.add("org.jacoco"); // To support JaCoCo code coverage tools
     packages.add("org.hamcrest"); // Since this package is referenced directly from org.junit