Change some smart_ptr == 0 to smart_ptr == nullptr.  Fixes http://llvm.org/bugs/show_bug.cgi?id=12185.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@152240 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/locale b/include/locale
index 2bdae30..f6d3860 100644
--- a/include/locale
+++ b/include/locale
@@ -3561,7 +3561,7 @@
             __throw_bad_alloc();
         __hn.reset(__bb);
         __hd.reset((char_type*)malloc(__n * sizeof(char_type)));
-        if (__hd == 0)
+        if (__hd == nullptr)
             __throw_bad_alloc();
         __db = __hd.get();
     }