Despite the doc not mentionning it, core.{proxies,frontends,backends}
methods are also available from init context.
(through core.register_init() functions)

Updating the documentation to reflect this possibility.

Adding a new lua class: Queue.

This class provides a generic FIFO storage mechanism that may be shared
between multiple lua contexts to easily pass data between them, as stock
Lua doesn't provide easy methods for passing data between multiple
coroutines.

New Queue object may be obtained using core.queue()
(it works like core.concat() for a concat Class)

Lua documentation was updated (including some usage examples)

Proxy mailers, which are configured using "email-alert" directives
in proxy sections from the configuration, are now being exposed
directly in lua thanks to the proxy:get_mailers() method which
returns a class containing the various mailers settings if email
alerts are configured for the given proxy (else nil is returned).

Both the class and the proxy method were marked as LEGACY since this
feature relies on mailers configuration, and the goal here is to provide
the last missing bits of information to lua scripts in order to make
them capable of sending email alerts instead of relying on the soon-to-
be deprecated mailers implementation based on checks (see src/mailers.c)

Lua documentation was updated accordingly.

Exposing a new hlua function, available from body or init contexts, that
forcefully disables the sending of email alerts even if the mailers are
defined in haproxy configuration.

This will help for sending email directly from lua.
(prevent legacy email sending from intefering with lua)

Exposing SERVER_CHECK event through the lua API.

New lua class named ServerEventCheck was added to provide additional
data for SERVER_CHECK event.

Lua documentation was updated accordingly.

Exposing SERVER_ADMIN event in lua and updating the documentation.

Exposing SERVER_STATE event in lua and updating the documentation.

This is to make ServerEvent class easier to understand,
some additional info related to ServerEvent class may be
included here.

Proxy.get_srv_act: number of active servers that are eligible for LB
Proxy.get_srv_bck: number of backup servers that are eligible for LB

Server.get_pend_conn: number of pending connections to the server
Server.get_cur_sess: number of current sessions handled by the server

Lua documentation was updated accordingly.