Add package upquote

[koppor]

I think, upquote is a useful package for listings. Should we just add \usepacakge{upquote} as default?

See https://tex.stackexchange.com/a/341057/9075 for more information.

[sieversMartin]

Well, I personally have been using it for years now. So, why not?
We could just use the upquote option of the listings package. However both solutions rely on textcomp, so we probably have to add a switch for pdflatex here.