Better fix for isfinite problem - works in older gcc's too.

Previous fix relying on __cplusplus value didn't fix for older
gcc's on linux, but this fix does.

intern/elbeem/intern/isosurface.cpp

@@ -15,20 +15,19 @@
 #include "particletracer.h"
 #include <algorithm>
 #include <stdio.h>
+#include <cmath>
 
 #ifdef sun
 #include "ieeefp.h"
 #endif
 
-#if  __cplusplus < 201103L
-#define isfinite finite
-#endif
-
 // just use default rounding for platforms where its not available
 #ifndef round
 #define round(x) (x)
 #endif
 
+using std::isfinite;
+
 /******************************************************************************
  * Constructor
  *****************************************************************************/