extract travis installs from build-depends automatically

I forgot to add libgtest-dev to the list of packages to install on
travis, so this slightly hacky oneliner might prevent us from having
the same problem again if we happen to change dependencies again.

Git-Dch: Ignore
support dist-upgrade options in full-upgrade

dist-upgrade is supposed to be an alias for full-upgrade in apt, but
dist-upgrade was the only command recognized of the two in the option
and flags recognition code.