Use a Myers Singleton for null
Avoid some static initialization problems.
From @marklakata
See #488
diff --git a/include/json/value.h b/include/json/value.h
index 4c29382..fb88c18 100644
--- a/include/json/value.h
+++ b/include/json/value.h
@@ -190,6 +190,8 @@
static const Value& null; ///< We regret this reference to a global instance; prefer the simpler Value().
static const Value& nullRef; ///< just a kludge for binary-compatibility; same as null
+ static Value const& nullSingleton(); ///< Prefer this to null or nullRef.
+
/// Minimum signed integer value that can be stored in a Json::Value.
static const LargestInt minLargestInt;
/// Maximum signed integer value that can be stored in a Json::Value.