Add missing include for calloc/free.

Bug: http://b/15193147
Change-Id: Ibb2fb6fef4ca6a23eb2f53111c4b01847fe468b2
diff --git a/hwcomposer.cpp b/hwcomposer.cpp
index f2e04b4..4256998 100644
--- a/hwcomposer.cpp
+++ b/hwcomposer.cpp
@@ -20,10 +20,13 @@
 
 #include <errno.h>
 #include <fcntl.h>
-#include <list>
 #include <pthread.h>
+#include <stdlib.h>
 #include <sys/param.h>
 #include <sys/resource.h>
+
+#include <list>
+
 #include <xf86drm.h>
 #include <xf86drmMode.h>