Fix for test_hwm_pubsub

Problem: test_proxy_hwm randomly fails

Solution: allow for a range between the minimum and maximum expected.
With 2 queues, that's between 20 and 40 messages depending on the
scheduling of the 3 threads involved.

Solution: use atomics to avoid issues on non-x86 architectures

Improve test reliability by: a) using XPUB in place of PUB to ensure …

Improve test reliability by: a) using XPUB in place of PUB to ensure we start publishing only after 1st subscriber has joined; b) accept both 2*HWM, 3*HWM and 4*HWM as TX/RX count of messages

add relicensing grant

Add new HWM tests and more detailed documentation

fix static build with libatomic

Create RELICENSE/FabriceFontaine.md
Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>

Commit 2ec5a33f added support to link
with -latomic if needed however using LDFLAGS doesn't work when
statically linking because LDFLAGS is added before LIBS

Detection of atomic fails with:

configure:23230: /accts/mlweber1/instance-2/output/host/bin/sparc-linux-g++ -o conftest -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64  -Os   -static -static -pedantic -Werror -Wall -D_GNU_SOURCE -D_REENTRANT -D_THREAD_SAFE -Wno-long-long -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64  -static -latomic conftest.cpp -lrt -lpthread -lstdc++ >&5
/tmp/ccgrvVTg.o: In function `main':
conftest.cpp:(.text.startup+0x10): undefined reference to `__atomic_fetch_add_4'
collect2: error: ld returned 1 exit status

So use LIBS instead of LDFLAGS

Fixes:
 - http://autobuild.buildroot.net/results/c471d6b1061a8516f7772735e471db68a32965aaSigned-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>

RELICENSE: Christoph Schulz

CMake cleanup

- Lowercase all commands
- Unify indent to 2 spaces
- Remove spaces around brackets
- Remove repitition of condition in else(...) and endif(...)

Note: (re-)running CMake did not change the content of the generated files

RELICENSE: Byron Mallett

Added relicensing permission from Byron Mallett

Solution: fix them

* Added SO_REUSEPORT socket option for UDP multicast recv ports

Revert "Problem: test_proxy not yet using unity"

This reverts commit fd27324e.

Migrate tests to unity, reduce duplication

Solution: migrate to unity

Solution: merge into a single test_use_fd and reduce code duplication by extracting common functions

Solution: migrate to unity

Solution: migrate to unity

Solution: migrate to unity

Solution: migrate to unity

Solution: migrate to unity

Fix build failure on ARM due to bad variable name

The variable decrement was changed to decrement_
in c581f43c

In -one- place, it remained as decrement
and gives:

In file included from src/ctx.hpp:44:0,
from src/address.cpp:33:
src/atomic_counter.hpp: In member function 'bool zmq::atomic_counter_t::sub(zmq::atomic_counter_t::integer_t)':
src/atomic_counter.hpp:191:28: error: 'decrement' was not declared in this scope

Changing it to decrement_ fixes the problem.

Migrate further tests to unity

Solution: use utilities from testutil_unity, reduce duplication

Solution: migrate to unity

Solution: migrate to unity

Solution: migrate to unity

Solution: extracted into common method