Start making RS 64-bit clean.

Change-Id: Ie40ad9a1d2b59094c86eb7e40b358e60120ce213
diff --git a/cpp/Allocation.cpp b/cpp/Allocation.cpp
index 4368225..7755f74 100644
--- a/cpp/Allocation.cpp
+++ b/cpp/Allocation.cpp
@@ -317,7 +317,7 @@
                                                 RsAllocationMipmapControl mips, uint32_t usage,
                                                 void *pointer) {
     void *id = rsAllocationCreateTyped(rs->getContext(), type->getID(), mips, usage,
-                                       (uint32_t)pointer);
+                                       (uintptr_t)pointer);
     if (id == 0) {
         ALOGE("Allocation creation failed.");
     }