Add <cstddef> include to get ptrdiff_t, for gcc-4.6; patch by Dimitry Andric.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@105994 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/ARMConstantPoolValue.h b/lib/Target/ARM/ARMConstantPoolValue.h
index 6f4eddf..3119b54 100644
--- a/lib/Target/ARM/ARMConstantPoolValue.h
+++ b/lib/Target/ARM/ARMConstantPoolValue.h
@@ -15,6 +15,7 @@
 #define LLVM_TARGET_ARM_CONSTANTPOOLVALUE_H
 
 #include "llvm/CodeGen/MachineConstantPool.h"
+#include <cstddef>
 
 namespace llvm {