This should have been done a *long* time ago, back when I initially
added Websocket support. This is the first part of two in improving
loop handler support with regards to socket closure.
Reason may include: {normal, shutdown} for the most normal shutdown,
{normal, timeout} for a loop handler timeout shutdown, or {error, _}
if an error occured.
This commit prevents erlang messages from keeping a websocket connection
alive. Previously, the timer was canceled upon any activity. Now, the
timeout is only canceled when actual data is sent from the client. The
handler_loop_timeout/1 function is called from websocket_data/4 instead
of handler_before_loop/4. It is also called after every successful reply
in handler_call/4.
