Problem: several fields are non-const without need

 Problem: unreachable code around socket_base_t::add/remove_signaler

fix Windows Intel compiler build failure

Solution: add const where easily possible

Solution: replaced by assertion

Problem: inconsistent formatting

Revert "Problem: Windows Intel compiler build broken"

Problem: Windows Intel compiler build broken

Solution: fix CMAKE_MODULES_PATH

Solution: fix execution directory

Solution: explicitly select clang-5.0

Solution: restrict to src, tests, perf, tools and include directories

Solution: add clang-format to cmake, and add another travis-ci build type

Solution: applied clang-format

Solution: added .clang-format file

Problem:  ZMQ_DISH triggers assert when hitting the watermark(?)

Solves issue #2907 by checking whether the msg already has a group

Improve handling of Jenkinsfile failed testlog archives

Port from zproject / czmq : Jenkinsfile :
* add RETRY_NUMBER suffix to test-suite tarballs
* and set build UNSTABLE if retries were needed

Problem: in case of exhausted resources on creation of a context, assertions are triggered

Solution: signal error to caller, and apply appropriate cleanup

Update Jenkinsfile according to current zproject template

Jenkinsfile : regenerated with zproject support for better workspace cleanup before test preparation

Enable ccache for faster builds

Problem: add_fd might be called with fd_ == retired_fd

Solution: add assertion

Correct linking for libzmq-static

all calls to target_link_libraries are now at the same location

Fix inclusion of cmake files in dists