port: Add isinf and isnan implementations for Visual Studio.

configure

@@ -12803,6 +12803,8 @@ esac
 ac_save_CFLAGS="$CFLAGS"
 CFLAGS="$CFLAGS $BUILTINFLAG"
 for ac_func in \
+	_finite \
+	_isnan \
 	_pclose \
 	_popen \
 	_snprintf \

configure.ac

@@ -1939,6 +1939,8 @@ dnl **** Check for functions ****
 ac_save_CFLAGS="$CFLAGS"
 CFLAGS="$CFLAGS $BUILTINFLAG"
 AC_CHECK_FUNCS(\
+	_finite \
+	_isnan \
 	_pclose \
 	_popen \
 	_snprintf \

include/config.h.in

@@ -1151,6 +1151,12 @@
 /* Define to 1 if you have the <zlib.h> header file. */
 #undef HAVE_ZLIB_H
 
+/* Define to 1 if you have the `_finite' function. */
+#undef HAVE__FINITE
+
+/* Define to 1 if you have the `_isnan' function. */
+#undef HAVE__ISNAN
+
 /* Define to 1 if you have the `_pclose' function. */
 #undef HAVE__PCLOSE
 

libs/port/isinf.c

@@ -31,6 +31,14 @@ int isinf(double x)
   return (!(finite(x) || isnand(x)));
 }
 
+#elif defined(HAVE_FLOAT_H) && defined(HAVE__ISNAN) && defined(HAVE__FINITE)
+#include <float.h>
+
+int isinf(double x)
+{
+  return (!(_finite(x) || _isnan(x)));
+}
+
 #else
 #error No isinf() implementation available.
 #endif

libs/port/isnan.c

@@ -31,6 +31,14 @@ int isnan(double x)
   return isnand(x);
 }
 
+#elif defined(HAVE_FLOAT_H) && defined(HAVE__ISNAN)
+#include <float.h>
+
+int isnan(double x)
+{
+  return _isnan(x);
+}
+
 #else
 #error No isnan() implementation available.
 #endif