Put the new warning from revision 133196 on NULL arithmetic behind the flag -Wnull-arthimetic and set to DefaultIgnore.  A few edge cases need to be worked out before this can be set to default.

llvm-svn: 133287
diff --git a/clang/test/SemaObjCXX/null_objc_pointer.mm b/clang/test/SemaObjCXX/null_objc_pointer.mm
index 1dadabe..0da9e50 100644
--- a/clang/test/SemaObjCXX/null_objc_pointer.mm
+++ b/clang/test/SemaObjCXX/null_objc_pointer.mm
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify %s
+// RUN: %clang_cc1 -fsyntax-only -verify -Wnull-arithmetic %s
 #define NULL __null
 
 @interface X