MINOR: lua: channel: add "channel" class

The channel class permits manipulation of channels. A channel is
an FIFO buffer between the client and the server. This class provides
function to read, write, forward, destroy and alter data between
the input and the ouput of the buffer.
diff --git a/include/types/hlua.h b/include/types/hlua.h
index 4925155..d0e0348 100644
--- a/include/types/hlua.h
+++ b/include/types/hlua.h
@@ -10,6 +10,7 @@
 #define CLASS_CORE     "Core"
 #define CLASS_TXN      "TXN"
 #define CLASS_SOCKET   "Socket"
+#define CLASS_CHANNEL  "Channel"
 
 struct session;
 
@@ -113,4 +114,11 @@
 	luaL_Buffer b; /* buffer used to prepare strings. */
 };
 
+/* This struct is used join to the class "channel". It
+ * just contains a pointer to the manipulated channel.
+ */
+struct hlua_channel {
+	struct channel *chn;
+};
+
 #endif /* _TYPES_HLUA_H */