Solution: instead of using a temporary release branch that gets
deleted after an arbitrary timer, which never matches the time OBS
actually takes to do a full git clone, keep the branch permanently
in place and simply move it forward to the latest tag on each
release.

Solution: add new tokens to .travis.yml and change ci_deploy.sh
script to use Github APIs to create a temporary branch at the tag,
and the OBS APIs to trigger a source service run in the stable and
draft release projects:
network:messaging:zeromq:release-stable
network:messaging:zeromq:release-draft

The branch hack is unfortunately necessary as it is not possible to
modify OBS sources with the token APIs, and it is also not possible
to automatically fetch the latest tag in the service files.
The temporary branch is immediately deleted.

Solution: Use travis to deploy these artifacts automatically.

The deployment is triggered by tagging on the zeromq/libzmq repository.
Of the many builds travis is checking only the default one with
libsodium and drafts disabled is used for deployment.

For now the results of `make distcheck` are deployed as well as their
md5 and sha1 hash sums. Further changes may upload a generated
Changelog as well.