Travis CI: install "libjack-jackd2-dev" for Linux builds
Travis CI: install "libjack-jackd2-dev" for Linux builds

Lartza/mumble,Lartza/mumble,Lartza/mumble,Lartza/mumble,Lartza/mumble,Lartza/mumble,Lartza/mumble,Lartza/mumble