Fix Casting

Stop a gcc warning about casting away const.

llvm-svn: 172465
diff --git a/llvm/lib/IR/Use.cpp b/llvm/lib/IR/Use.cpp
index 481cbab..1d343e8 100644
--- a/llvm/lib/IR/Use.cpp
+++ b/llvm/lib/IR/Use.cpp
@@ -139,7 +139,7 @@
   const UserRef *ref = reinterpret_cast<const UserRef*>(End);
   return ref->getInt()
     ? ref->getPointer()
-    : (User*)End;
+    : reinterpret_cast<User*>(const_cast<Use*>(End));
 }
 
 } // End llvm namespace