Make text format non-normative.

chapters/packages.tex

@@ -349,10 +349,11 @@ \section{Multilingual Descriptions}\label{multilingual-descriptions}
 \end{enumerate}
 
 The files consist of a header and a body.
+The detailed format of these files is described in \href{https://www.gnu.org/software/gettext/manual/gettext.pdf}{GNU gettext}.
+\begin{nonnormative}
 All text strings are in double quotes and encoded with UTF-8 characters.
 Comments start with an \lstinline!#! and are continued until the end of line.
 Spaces outside strings are ignored and used as separators.
-The detailed format of these files is described in \href{https://www.gnu.org/software/gettext/manual/gettext.pdf}{GNU gettext}.
 
 The header is marked with an empty \emph{msgid} entry and looks like this:
 \begin{lstlisting}
@@ -384,10 +385,11 @@ \section{Multilingual Descriptions}\label{multilingual-descriptions}
 msgid "<descriptive text>"
 msgstr "<translation>"
 \end{lstlisting}
+\end{nonnormative}
 Only the keywords \lstinline!msgctxt!, \lstinline!msgid! and \lstinline!msgstr! are used.
 
 At first there can be an optional comment describing the location (file name and line number) of the text to translate.
- Multiple occurences of the same string can be listed here, separated by space.
+Multiple occurences of the same string can be listed here, separated by space.
 
 Then, the \lstinline!<context identifier>! behind the keyword \lstinline!msgctxt! is the full name of the Modelica class (e.g., \lstinline!Modelica.Blocks.Math.Sin!) where the text appears in.
 Short class definitions do not appear here.