Fix for the cfd benchmark

Added an include needed for correctly invoking the free primitive and
added namespace for the rand function (problems only on the odroid XU3)

opencl/cfd/util.h

@@ -1,5 +1,6 @@
 #ifndef _C_UTIL_
 #define _C_UTIL_
+#include <cstdlib>
 #include <math.h>
 #include <iostream>
 #include <omp.h>
@@ -69,7 +70,7 @@ double gettime() {
 template<typename datatype>
 void fill(datatype *A, const int n, const datatype maxi){
     for (int j = 0; j < n; j++){
-        A[j] = ((datatype) maxi * (rand() / (RAND_MAX + 1.0f)));
+        A[j] = ((datatype) maxi * (std::rand() / (RAND_MAX + 1.0f)));
     }
 }