Fix compile error after recent 9c2bbfb6 commit.

Older C++ compilers use finite instead of isfinite.

intern/elbeem/intern/isosurface.cpp

@@ -20,6 +20,10 @@
 #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)