Turn -Wnull-arithmetic back on by default -- we now have tests for the

false positives, including those in the GCC test suite, and don't warn
about them.

Let me know if this causes fallout, we can turn it back off if needed.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@133384 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Basic/DiagnosticSemaKinds.td

@@ -2999,7 +2999,7 @@ def warn_comparison_of_mixed_enum_types : Warning<
   InGroup<DiagGroup<"enum-compare">>;
 def warn_null_in_arithmetic_operation : Warning<
   "use of NULL in arithmetic operation">,
-  InGroup<DiagGroup<"null-arithmetic">>, DefaultIgnore;
+  InGroup<DiagGroup<"null-arithmetic">>;
 
 def err_invalid_this_use : Error<
   "invalid use of 'this' outside of a nonstatic member function">;