GCC 4.3 and later needs an extra #include <cstring>.

--- a/DBP/src/op.cc
+++ b/DBP/src/op.cc
@@ -22,6 +22,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <sys/stat.h>
+#include <cstring>
 
 using namespace Dbp;
 
