Allow mixing of thread offsets between 32 and 64bit architectures.

Begin a more full implementation x86-64 REX prefixes.
Doesn't implement 64bit thread offset support for the JNI compiler.

Change-Id: If9af2f08a1833c21ddb4b4077f9b03add1a05147
diff --git a/runtime/entrypoints/interpreter/interpreter_entrypoints.h b/runtime/entrypoints/interpreter/interpreter_entrypoints.h
index c7df4e6..d8b2204 100644
--- a/runtime/entrypoints/interpreter/interpreter_entrypoints.h
+++ b/runtime/entrypoints/interpreter/interpreter_entrypoints.h
@@ -21,9 +21,8 @@
 #include "dex_file.h"
 #include "offsets.h"
 
-#define INTERPRETER_ENTRYPOINT_OFFSET(x) \
-    ThreadOffset(static_cast<uintptr_t>(OFFSETOF_MEMBER(Thread, interpreter_entrypoints_)) + \
-                 static_cast<uintptr_t>(OFFSETOF_MEMBER(InterpreterEntryPoints, x)))
+#define INTERPRETER_ENTRYPOINT_OFFSET(ptr_size, x) \
+    Thread::InterpreterEntryPointOffset<ptr_size>(OFFSETOF_MEMBER(InterpreterEntryPoints, x))
 
 namespace art {