don't define commands for dune-fem and dune-disc. They are not used anywhere

[[Imported from SVN: r6479]]

doc/buildsystem/buildsystem.tex

@@ -35,8 +35,6 @@
 \newcommand{\dunecommon}{\texttt{dune-common}\xspace}
 \newcommand{\duneistl}{\texttt{dune-istl}\xspace}
 \newcommand{\dunegrid}{\texttt{dune-grid}\xspace}
-\newcommand{\dunefem}{\texttt{dune-fem}\xspace}
-\newcommand{\dunedisc}{\texttt{dune-disc}\xspace}
 \newcommand{\dunegridhowto}{\texttt{dune-grid-howto}\xspace}
 \newcommand{\dunegriddevhowto}{\texttt{dune-grid-dev-howto}\xspace}
 \newcommand{\dunecontrol}{\texttt{dunecontrol}\xspace}