Add getPointer for USAGE_SHARED allocations.

Change-Id: I13a2af09bbbeec6cc6131b935979ac21c02820be
diff --git a/cpp/rsCppStructs.h b/cpp/rsCppStructs.h
index 70931be..6c14e8c 100644
--- a/cpp/rsCppStructs.h
+++ b/cpp/rsCppStructs.h
@@ -559,6 +559,13 @@
                                         uint32_t usage = RS_ALLOCATION_USAGE_SCRIPT);
 
 
+    /**
+     * Get the backing pointer for a USAGE_SHARED allocation.
+     * @param[in] stride optional parameter. when non-NULL, will contain
+     *   stride in bytes of a 2D Allocation
+     * @return pointer to data
+     */
+    void * getPointer(size_t *stride = NULL);
 };
 
  /**