use of invalid L in libevent wrapper from Lua Programming Gems

[Sam Roberts <vieuxtech@...>]

The wrapper in gem 27 doesn't use L as passed to priv.dispatch(),
instead it uses some previously-valid L.

Cheers,
Sam

This code segfaults:

require "Event"

local function callback(event, fd, event_type)
end

local creator = coroutine.wrap(function()
    return Event.create(0, Event.EV_READ, callback)
end)

event = creator()
event:add(1)
Event.dispatch()