ci: add tests
Add to .gitlab.ci.yml test_linux, test_debian_docker_luacheck, coverage from .travis.mk. Add checkpatch.
NO_DOC=ci change NO_TEST=ci change NO_CHANGELOG=ci change
Add to .gitlab.ci.yml test_linux, test_debian_docker_luacheck, coverage from .travis.mk. Add checkpatch.
NO_DOC=ci change NO_TEST=ci change NO_CHANGELOG=ci change