Fix memory leak

Function GridManager::createGrdecl() generally allocates memory
(using std::malloc()) for the MAPAXES keyword data output of the
'grdecl' structure.  Release those resources before leaving the
scope to prevent memory leak introduced in commit fdca540.

examples/sim_fibo_ad_cp.cpp

@@ -73,6 +73,7 @@
 
 #include <memory>
 #include <algorithm>
+#include <cstdlib>
 #include <iostream>
 #include <vector>
 #include <numeric>
@@ -130,6 +131,8 @@ try
         GridManager::createGrdecl(newParserDeck, g);
 
         grid->processEclipseFormat(g, 2e-12, false);
+
+        std::free(const_cast<double*>(g.mapaxes));
     }