Add libghc-mtl-dev to ubuntu-precise; resolves travis-ci/apt-package-whitelist#1662
Add libghc-mtl-dev to ubuntu-precise; resolves travis-ci/apt-package-whitelist#1662

Packages: libghc-mtl-dev libghc-mtl-prof libghc-mtl-doc

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