Add libvpx-dev to ubuntu-precise; resolves travis-ci/apt-package-whitelist#2386
Add libvpx-dev to ubuntu-precise; resolves travis-ci/apt-package-whitelist#2386

Packages: libvpx-dev libvpx3 libvpx3-dbg libvpx-doc vpx-tools

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