Move rs.h includes to source files.

Change-Id: Ic49e3fa5580c67f35a21f95872794ea03dd114b6
diff --git a/cpp/Element.cpp b/cpp/Element.cpp
index 198aac8..f3e83d0 100644
--- a/cpp/Element.cpp
+++ b/cpp/Element.cpp
@@ -18,6 +18,7 @@
 #include <string.h>
 
 #include "RenderScript.h"
+#include <rs.h>
 
 using namespace android;
 using namespace RSC;