Cleanup includes for rs/cpp to not expose internal details.

Change-Id: Ib23f591f8418d3318f61ab1d3f6f2b684bf95692
diff --git a/cpp/Sampler.cpp b/cpp/Sampler.cpp
index bf99125..500651f 100644
--- a/cpp/Sampler.cpp
+++ b/cpp/Sampler.cpp
@@ -15,6 +15,7 @@
  */
 
 #include "RenderScript.h"
+#include "rsCppInternal.h"
 
 using namespace android;
 using namespace RSC;