.travis.yml: Only test master and "smoke-me" branches

Signed-off-by: Niels Thykier <niels@thykier.net>
.travis.yml: Run the current lintian on itself

... instead of installing the Ubuntu from the repositories.

Signed-off-by: Niels Thykier <niels@thykier.net>
hardening-info: Discard STDERR from hardening

Signed-off-by: Niels Thykier <niels@thykier.net>
t/runtests: Fix potential error-hiding bug

Signed-off-by: Niels Thykier <niels@thykier.net>
t/runtests: Dump build logs on test failures in t/tests

Signed-off-by: Niels Thykier <niels@thykier.net>