Generic JNI implementation for x86_64

Starting implementation for generic JNI on x86_64. Frames are of
large static size (>4K) right now, should be compacted later. Passes
the whole of jni_compiler_test.

Change-Id: I88ac3e13a534afe7568d62a1ef97cb766e8260e4
diff --git a/runtime/thread.h b/runtime/thread.h
index 6df2b1c..c7ab735 100644
--- a/runtime/thread.h
+++ b/runtime/thread.h
@@ -320,8 +320,7 @@
 
   ThrowLocation GetCurrentLocationForThrow() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
-  void SetTopOfStack(void* stack, uintptr_t pc) {
-    mirror::ArtMethod** top_method = reinterpret_cast<mirror::ArtMethod**>(stack);
+  void SetTopOfStack(mirror::ArtMethod** top_method, uintptr_t pc) {
     managed_stack_.SetTopQuickFrame(top_method);
     managed_stack_.SetTopQuickFramePc(pc);
   }