From: Stig Sandbeck Mathisen <ssm@debian.org>
Subject: Include unistd.h to support building with gcc/g++ 4.7

--- a/util/logfile.cc
+++ b/util/logfile.cc
@@ -49,6 +49,7 @@
 #include <sstream>
 #include <sys/stat.h>
 #include <sys/types.h>
+#include <unistd.h>
 
 namespace datadifferential {
 namespace util {