Add ghc-7.6.1 to ubuntu-precise; resolves travis-ci/apt-package-whitelist#3298
Add ghc-7.6.1 to ubuntu-precise; resolves travis-ci/apt-package-whitelist#3298

Packages: ghc-7.6.1 ghc-7.6.1-prof ghc-7.6.1-dyn ghc-7.6.1-htmldocs

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