Rename 'MAX_LEN' to 'MAX_PACKET_LEN'

include/emqttd_protocol.hrl

@@ -129,11 +129,16 @@
 
 -type(mqtt_connack() :: ?CONNACK_ACCEPT..?CONNACK_AUTH).
 
+%%--------------------------------------------------------------------
+%% Max MQTT Packet Length
+%%--------------------------------------------------------------------
+
+-define(MAX_PACKET_LEN, 16#fffffff).
+
 %%--------------------------------------------------------------------
 %% MQTT Parser and Serializer
 %%--------------------------------------------------------------------
 
--define(MAX_LEN, 16#fffffff).
 -define(HIGHBIT, 2#10000000).
 -define(LOWBITS, 2#01111111).