isinf and isnan are macros, not functions; fix configure script
to use AC_CHECK_DECLS instead of AC_CHECK_FUNCS for these.
(See discussion in issue #4506)
diff --git a/Include/pymath.h b/Include/pymath.h
index 7cea9ae..13f95b4 100644
--- a/Include/pymath.h
+++ b/Include/pymath.h
@@ -87,7 +87,7 @@
* Note: PC/pyconfig.h defines Py_IS_NAN as _isnan
*/
#ifndef Py_IS_NAN
-#ifdef HAVE_ISNAN
+#ifdef HAVE_DECL_ISNAN
#define Py_IS_NAN(X) isnan(X)
#else
#define Py_IS_NAN(X) ((X) != (X))
@@ -104,7 +104,7 @@
* Note: PC/pyconfig.h defines Py_IS_INFINITY as _isinf
*/
#ifndef Py_IS_INFINITY
-#ifdef HAVE_ISINF
+#ifdef HAVE_DECL_ISINF
#define Py_IS_INFINITY(X) isinf(X)
#else
#define Py_IS_INFINITY(X) ((X) && (X)*0.5 == (X))