Fix isfinite() checks to work with all C++11 compilers

Fixes https://github.com/swig/swig/issues/615,
https://github.com/swig/swig/pull/788 and https://github.com/swig/swig/pull/849.

CHANGES.current

@@ -5,6 +5,11 @@ See the RELEASENOTES file for a summary of changes in each release.
 Version 3.0.11 (in progress)
 ============================
 
+2016-12-21: olly
+	    Fix isfinite() checks to work with all C++11 compilers.
+	    Fixes https://github.com/swig/swig/issues/615, https://github.com/swig/swig/pull/788
+	    and https://github.com/swig/swig/pull/849.
+
 2016-12-20: wsfulton
             %namewarn unnecessarily caused keyword warnings for non-instantiated template classes
             and duplicate warnings for instantiated template classes when keywords were used.

Lib/typemaps/fragments.swg

@@ -168,11 +168,23 @@
 %fragment("SWIG_isfinite","header",fragment="<math.h>,<float.h>") %{
 /* Getting isfinite working pre C99 across multiple platforms is non-trivial. Users can provide SWIG_isfinite on older platforms. */
 #ifndef SWIG_isfinite
-/* isfinite() is a macro for C99, but a function in namespace std for C++11. */
+/* isfinite() is a macro for C99 */
 # if defined(isfinite)
 #  define SWIG_isfinite(X) (isfinite(X))
 # elif defined __cplusplus && __cplusplus >= 201103L
-#  define SWIG_isfinite(X) (std::isfinite(X))
+/* Use a template so that this works whether isfinite() is std::isfinite() or
+ * in the global namespace.  The reality seems to vary between compiler
+ * versions.
+ *
+ * Make sure namespace std exists to avoid compiler warnings.
+ */
+namespace std { }
+template<typename T>
+inline int SWIG_isfinite_func(T x) {
+  using namespace std;
+  return isfinite(x);
+}
+#  define SWIG_isfinite(X) (SWIG_isfinite_func(X))
 # elif defined(_MSC_VER)
 #  define SWIG_isfinite(X) (_finite(X))
 # elif defined(__sun) && defined(__SVR4)