COMP:  Use C++11 override directly

The override support in C++11 is required so avoid aliasing
this feature.  Compilers that do not support the override keyword
are no longer supported.
diff --git a/include/json/reader.h b/include/json/reader.h
index 9a7fba2..58cb58b 100644
--- a/include/json/reader.h
+++ b/include/json/reader.h
@@ -347,9 +347,9 @@
   Json::Value settings_;
 
   CharReaderBuilder();
-  ~CharReaderBuilder() JSONCPP_OVERRIDE;
+  ~CharReaderBuilder() override;
 
-  CharReader* newCharReader() const JSONCPP_OVERRIDE;
+  CharReader* newCharReader() const override;
 
   /** \return true if 'settings' are legal and consistent;
    *   otherwise, indicate bad settings via 'invalid'.