http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=550303

Patch by Cyril Brulebois <kibi@debian.org>

diff --git a/libs/hydrogen/src/hydrogen.cpp b/libs/hydrogen/src/hydrogen.cpp
--- a/libs/hydrogen/src/hydrogen.cpp
+++ b/libs/hydrogen/src/hydrogen.cpp
@@ -37,6 +37,7 @@
 #include <iostream>
 #include <ctime>
 #include <cmath>
+#include <cstdlib>
 
 #include <QtCore/QMutex>
 #include <QtCore/QMutexLocker>