Add ghc-7.4.2 to ubuntu-precise; resolves travis-ci/apt-package-whitelist#3233
Add ghc-7.4.2 to ubuntu-precise; resolves travis-ci/apt-package-whitelist#3233

Packages: ghc-7.4.2 ghc-7.4.2-prof ghc-7.4.2-dyn ghc-7.4.2-htmldocs

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