Add _init() and _free() for cipher modules

include/polarssl/aes.h

@@ -73,6 +73,20 @@ typedef struct
 }
 aes_context;
 
+/**
+ * \brief          Initialize AES context
+ *
+ * \param ctx      AES context to be initialized
+ */
+void aes_init( aes_context *ctx );
+
+/**
+ * \brief          Clear AES context
+ *
+ * \param ctx      AES context to be cleared
+ */
+void aes_free( aes_context *ctx );
+
 /**
  * \brief          AES key schedule (encryption)
  *