Fix for zcert_new calling zmq_curve_keypair.

Was passing an insufficiently sized buffer
Merge pull request #701 from hintjens/master

Clean up zring, add zsock_flush
Merge pull request #704 from twhittock/master

Fix for zcert_new calling zmq_curve_keypair.
Fix issue #553 by providing explicit shutdown function.

Required as Windows dll shutdown order is not guaranteed - winsock
can be shut down before zmq, making atexit unusable on Windows
Merge pull request #705 from twhittock/master

Fix issue #553 by providing explicit shutdown function.
missing doc about zhash picture in zsock_send
add zmsg picture to zsock_send/recv
added test
fix typo: zsock_send changed contents from zmsg indicated in picture.  fixed.
Merge pull request #706 from mosconi/master

missing doc about zhash picture in zsock_send
Merge pull request #707 from mosconi/zsock_zmsg_picture

Zsock zmsg picture
zsock.c: declaring variable outside 'for'. Error on non-c99 compilers.
Merge pull request #710 from guidefloripa/master

zsock.c: declaring variable outside 'for'. Error on non-c99 compilers.
Make duplicator usage in zring consistent with use in zhash
Merge pull request #709 from Q-Leap-Networks/pull-consistent-duplicators

Make duplicator usage in zring consistent with use in zhash
zpubsub in labs area compiles to object files.
zpubsub examples build with zpubsub from labs area.
Merge pull request #711 from lovmoen/master

zpubsub in labs area compiles to object files.
Problem: Cumbersome to compile z* files in labs folder

Solution: Changed the autotools configuration

Prerequisites: libczmq is installed

Step 1: ./configure --enable-labs=yes
Step 2: make
Step 3: make install

Know you've got a library libczmq_labs installed on your system which
can be used in third party projects.
Merge pull request #713 from sappo/master

Problem: Cumbersome to compile z* files in labs folder
Problem: There's no example on how to use labs library

Solution:

* modify the zpubsub simple example to link against labs library.
* update the README.txt with Step by Step setup.