Compiling on Ubuntu 16.04 needs more libraries

[doppioandante]

Hello, I found out that libqtwebkit-dev and libraptor1-dev are needed to compile the dependencies, at least since Ubuntu 16.04 (which is the latest LTS).
Maybe it would be worth to add a different section or update the current one?

EDIT: I now see that raptor should have been built along, so the only one to be added is webkit.