build: fix compile problems pointed out by gcc 4.4
diff --git a/src/mem/physical.cc b/src/mem/physical.cc
index be4086c..121a6e4 100644
--- a/src/mem/physical.cc
+++ b/src/mem/physical.cc
@@ -36,6 +36,7 @@
 #include <unistd.h>
 #include <zlib.h>
 
+#include <cstdio>
 #include <iostream>
 #include <string>