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)

Problem: When building libzmq with CMake, the installed libzmq.dylib
  has a relative install name (otool -D libzmq.dylib) on MacOS. This
  is a regression against building via autotools which sets an
  absolute install name. Effectively, the CMake built libzmq.dylib
  is rendered useless if installed in non-system directories and
  used in environments without explicit DYLD_LIBRARY_PATH mgmt. For
  example running any of the installed executables currently fails:
  $ /some_install_prefix/bin/inproc_lat
  dyld: Library not loaded: libzmq.5.dylib
    Referenced from: /some_install_prefix/bin/inproc_lat
    Reason: image not found
  Trace/BPT trap: 5

Solution: Best practice is to install relocatable dylibs.
  On MacOS this means setting an install name with a special prefix,
  e.g. @rpath/libzmq.dylib, and adding the relevant search paths
  to the embedded rpath list. In this patch the necessary CMake options
  are added to generate the desired relocatable dylibs. Find more
  information on: https://cmake.org/Wiki/CMake_RPATH_handling.

Problem: Server-client not marked as DRAFT in manpage

Solution: add note like for radio-dish
Fixes: #3050

Fix fd_t variable casting on Windows platform

event_accepted() already accepts fd_t type and there is no reason to cast it to int type
Moreover, on Windows x64 this leads to truncation memsize -> int

configure.ac: serach for dladdr only on libunwind

The original configure.ac tries to check for dladdr, but it actually needs
it only in case we have libunwind (which has a another section and checks for it
too).
This can fail the build on systems without dynamic linking support.
Therefore, the dladdr check has to be preformed only when checking libunwind.
Signed-off-by: Asaf Kahlon <asafka7@gmail.com>

* Implement the wsa_error_no function with switch-case
Signed-off-by: Asaf Kahlon <asafka7@gmail.com>