Various things.

This patch:

1. adds good-enough implementations for a couple of Class native methods we
need.

2. removes a fixed TODO from image_test.

3. adds missing null checks to the Thread native methods, and forwards
Thread.nativeCreate to Thread::Create.

4. stops jni_compiler from overwriting already-registered native methods
with the dynamic lookup stub.

5. adds workarounds to Thread::CreatePeer so we can cope better without
code, attempts to initialize thread groups correctly, dumps thread state
from the managed peer (where one exists), and implements Thread::DumpStack
for debugging (and SIGQUIT dumps).

Change-Id: I3281226dd22ec852dca5165748fc75a254904ac0
diff --git a/src/runtime.cc b/src/runtime.cc
index 454a38c..a1157e6 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -413,7 +413,7 @@
   //REGISTER(register_dalvik_system_VMRuntime);
   REGISTER(register_dalvik_system_VMStack);
   //REGISTER(register_dalvik_system_Zygote);
-  //REGISTER(register_java_lang_Class);
+  REGISTER(register_java_lang_Class);
   REGISTER(register_java_lang_Object);
   REGISTER(register_java_lang_Runtime);
   REGISTER(register_java_lang_String);