Websocket: Also apply max_frame_size limit to decompressed data

Before this commit frames could "cheat" by compressing data
below the limit which would get expanded above the limit.
Now Cowboy will stop decompressing data when the limit is
reached.

test/ws_SUITE_data/ws_max_frame_size.erl

@@ -5,7 +5,7 @@
 -export([websocket_info/2]).
 
 init(Req, State) ->
-	{cowboy_websocket, Req, State, #{max_frame_size => 8}}.
+	{cowboy_websocket, Req, State, #{max_frame_size => 8, compress => true}}.
 
 websocket_handle({text, Data}, State) ->
 	{[{text, Data}], State};