Issue #21958: Define HAVE_ROUND when building with VS 2013 and above.
Patch by Zachary Turner.
diff --git a/PC/pyconfig.h b/PC/pyconfig.h
index 5a6acfc..e1c1988 100644
--- a/PC/pyconfig.h
+++ b/PC/pyconfig.h
@@ -436,6 +436,11 @@
 /* Define to 1 if you have the `copysign' function. */
 #define HAVE_COPYSIGN 1
 
+/* Define to 1 if you have the `round' function. */
+#if _MSC_VER >= 1800
+#define HAVE_ROUND 1
+#endif
+
 /* Define to 1 if you have the `isinf' macro. */
 #define HAVE_DECL_ISINF 1