bpo-26121: Use C library implementation for math functions erf() and erfc() on Windows. (#632)

Author: serhiy-storchaka

PC/pyconfig.h

@@ -684,4 +684,10 @@ Py_NO_ENABLE_SHARED to find out.  Also support MS_NO_COREDLL for b/w compat */
    least significant byte first */
 #define DOUBLE_IS_LITTLE_ENDIAN_IEEE754 1
 
+/* Define to 1 if you have the `erf' function. */
+#define HAVE_ERF 1
+
+/* Define to 1 if you have the `erfc' function. */
+#define HAVE_ERFC 1
+
 #endif /* !Py_CONFIG_H */