cleanup library and some basic tests. Includes, add guards to includes
diff --git a/include/polarssl/memory_buffer_alloc.h b/include/polarssl/memory_buffer_alloc.h
index 5f8e329..ab36b41 100644
--- a/include/polarssl/memory_buffer_alloc.h
+++ b/include/polarssl/memory_buffer_alloc.h
@@ -30,7 +30,7 @@
 #include POLARSSL_CONFIG_FILE
 #endif
 
-#include <stdlib.h>
+#include <stddef.h>
 
 /**
  * \name SECTION: Module settings