Add valac to ubuntu-precise; resolves travis-ci/apt-package-whitelist#1305
Add valac to ubuntu-precise; resolves travis-ci/apt-package-whitelist#1305

Packages: valac valac-0.28 valac-0.28-vapi vala-0.28-doc libvala-0.28-0 libvala-0.28-dev valac-0.28-dbg libvala-0.28-0-dbg

travis-ci/apt-package-whitelist,travis-ci/apt-package-whitelist