Implement getting of 64-bit locals (double, long).

Also implement the JDWP "GetClassLoader" request, used by jswat's "classes"
command.

Also implement the JDWP "exit" request, tested with jswat's "shutdown".

Change-Id: Ic8424a332151242211d8a772721deb3199b24682
diff --git a/src/java_lang_Class.cc b/src/java_lang_Class.cc
index cba037a..b85969e 100644
--- a/src/java_lang_Class.cc
+++ b/src/java_lang_Class.cc
@@ -195,7 +195,7 @@
 
 jobject Class_getClassLoader(JNIEnv* env, jclass, jobject javaClass) {
   Class* c = Decode<Class*>(env, javaClass);
-  Object* result = reinterpret_cast<Object*>(const_cast<ClassLoader*>(c->GetClassLoader()));
+  Object* result = c->GetClassLoader();
   return AddLocalReference<jobject>(env, result);
 }