Fix compilation of sortkeys.cpp with MSVC 2013 (hopefully).

example/sortkeys/sortkeys.cpp

@@ -45,9 +45,8 @@ int main() {
 // C++11 supports std::move() of Value so it always have no problem for std::sort().
 // Some C++03 implementations of std::sort() requires copy constructor which causes compilation error.
 // Needs a sorting function only depends on std::swap() instead.
-#if __cplusplus >= 201103L || !defined(__GLIBCXX__)
+#if __cplusplus >= 201103L || (!defined(__GLIBCXX__) && (!defined(_MSC_VER) || _MSC_VER >= 1900))
     std::sort(d.MemberBegin(), d.MemberEnd(), NameComparator());
-#endif
 
     printIt(d);
 
@@ -59,4 +58,5 @@ int main() {
   "zeta": false
 }
 */
+#endif
 }