try to suit ubuntu compile for quantify script

tools/quantification/convert.cpp

@@ -3,8 +3,8 @@
 #include "src/enforce.h"
 #include "src/var_desc.h"
 #include "src/program_desc.h"
+#include <cstring>
 #include <cstdlib>
-#include <string.h>
 #include <cmath>
 #include <iostream>
 #include <utility>
@@ -14,6 +14,7 @@
 #include <fstream>
 #include <iostream>
 #include <limits>
+#include <limits>
 
 
 const size_t kSize64 = sizeof(uint64_t);