Add missing includes.

Change-Id: Ie3acca064c1bcecb4e0305e61f01ba8cea4abe03
diff --git a/cpustats/cpustats.c b/cpustats/cpustats.c
index d720f5e..32d75b2 100644
--- a/cpustats/cpustats.c
+++ b/cpustats/cpustats.c
@@ -31,6 +31,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #include <unistd.h>
 
 #define MAX_BUF_SIZE 64