Add giflib-dbg in trusty to ubuntu-trusty; resolves travis-ci/apt-package-whitelist#4172
Add giflib-dbg in trusty to ubuntu-trusty; resolves travis-ci/apt-package-whitelist#4172

Packages: giflib-dbg giflib-tools libgif4 libgif-dev

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