ZeroMQ 3.x Input Plugin

Building this plugin:
Requires libzmq and libczmq. First, download the tarballs of both libzmq
and its supporting libczmq from http://download.zeromq.org. As of this
writing (04/23/2013), the most recent versions of libzmq and czmq are
3.2.2 and 1.3.2 respectively. Configure, build, and then install both libs.

Imzmq3 allows you to push data into rsyslog from a zeromq socket.  The example
below binds a SUB socket to port 7172, and then any messages with the topic
"foo" will be pushed into rsyslog.

Please note:
This plugin only supports the newer (v7) config format.  Legacy config support
was removed.

Example Rsyslog.conf snippet:
-------------------------------------------------------------------------------
module(load="imzmq3" ioThreads="1")
input(type="imzmq3" action="CONNECT" socktype="SUB" description="tcp://*:7172" subscribe="foo,bar")

-------------------------------------------------------------------------------
Note you can specify multiple subscriptions with a comma-delimited list, with 
no spaces between values.  

The only global parameter for this plugin is ioThreads, which is optional and
probably best left to the zmq default unless you know exactly what you are
doing.

The instance-level parameters are:

Required
description
subscribe (required if the sockType is SUB)

Optional
sockType (defaults to SUB)
action   (defaults to BIND
sndHWM   
rcvHWM
identity
sndBuf
rcvBuf
linger
backlog
sndTimeout
rcvTimeout
maxMsgSize
rate
recoveryIVL
multicastHops
reconnectIVL
reconnectIVLMax
ipv4Only
affinity

These all correspond to zmq optional settings.  Except where noted, the defaults
are the zmq defaults if not set.  See http://api.zeromq.org/3-2:zmq-setsockopt
for info on these.
