Move assembler out of runtime into compiler/utils.

Other directory layout bits of clean up. There is still work to separate quick
and portable in some files (e.g. argument visitor, proxy..).

Change-Id: If8fecffda8ba5c4c47a035f0c622c538c6b58351
diff --git a/runtime/stack.h b/runtime/stack.h
index 0b94f27..de93846 100644
--- a/runtime/stack.h
+++ b/runtime/stack.h
@@ -20,7 +20,7 @@
 #include "dex_file.h"
 #include "instrumentation.h"
 #include "base/macros.h"
-#include "oat/runtime/context.h"
+#include "arch/context.h"
 
 #include <stdint.h>
 #include <string>