Solution: add a new ZMQ_MULTICAST_LOOP option for UDP sockets.

Problem: test helper recv_string_expect_success ignores flags

Solution: pass the flags to zmq_recv

UDP Ipv6 support

Solution: Add IPv6 support

Add ip_resolver.cpp and ip_resolver.hpp for vs2015 libzmq project

acinclude.m4: check if -latomic is needed.

On some cases, -latomic is needed for likning, and since the current
acinclude.m4 checks only compilation we can sometimes miss the need for -latomic
and the linking process will fail.
Therefore, the AC_CHECK_IFELSE was replaced with AC_LINK_IFELSE. If the first
try fails, we try to link again with -latomic and add LIBS="-latmoic" in case we
succeeded.
Signed-off-by: Asaf Kahlon <asafka7@gmail.com>

Mcast bind

for multicast

Solution: augment the UDP URL syntax to accept an interface specifier with a
syntax similar to the PGM urls.

Fixes #2212

Solution: factor the code into ip_resolver, add IPv6 support and unit tests.

Udp parser

Solution: replace it with the ip_resolver code shared with the TCP
address code

It simplifies the UDP parsing code and makes it behave more like the
TCP counterpart, in particular it's not possible to connect to hosts
by name and bind by NIC names.

It also adds support for "*" port resolving to 0 (useful to let the OS
allocate the port number).

Solution: add unit tests

Problem: ip_resolver allows wildcard ports for non-bindable sockets

Solution: return an error in this situation but still allow using an explicit
"0" if somebody really wants to connect to port 0.

This shouldn't break any existing code because a "*" port was already rejected
in an early test in the TCP path in zmq::socket_base_t::connect.

Add me to AUTHORS + RELICENSE file

Problem: address parsing code is tied to the TCP code

Solution: Factor the code into a different file with a well defined API and add
unit tests.

More attempts to speed up Appveyor

Solution: use 2013 images for all builds bar 2, to test newer versions

Solution: cache the git repository and build directory

Solution: add -j flag to run them in paralle, cuts test runtime
from ~80 to ~20 seconds

Solution: set the equivalent flag

Update android_build_helper.sh

Update README.md

Minimum platform for arm is android-14

added missing = to export VARIABLE=VALUE

use HTTPS when downloading a binary before excuting it check hashes

Changed  the download URL to use HTTPS.
Provided the hashes for version r10e
Replaces /home/zmq by $HOME

Problem: heartbeat commands break REP session, unclear documentation

Solution: check more socket type to cover other session managers.
Increase timeout as the test now takes ~12 seconds.

Solution: ignore command messages in the REQ session to avoid
disrupting the state machine.
Commands are handled by the engine before handing off to the session.

Solution: mention in manpage that if the timeout is not set and the
interval is, the timeout will be equal to the interval

Fix formatting in CONTRIBUTING

Avoids the git instructions being all on one line.

Install relocatable dylibs (MacOS)