Add paragraph breaks around tabbing environment for LaTeXML build

Fixes modelica#3009.

chapters/functions.tex

@@ -2464,6 +2464,12 @@ \subsection{Annotations for External Libraries and Include Files}\label{annotati
 end MyExternalFunctions;
 \end{lstlisting}
 Directory structure:
+% Adding paragraph break above tabbing environment to work around LaTeXML issue:
+% - https://github.com/brucemiller/LaTeXML/issues/1719
+\ifpdf
+\else
+\par
+\fi
 {\upshape
 \begin{tabbing}
 \hspace{15em}\=\hspace{1em}\=\kill
@@ -2489,6 +2495,12 @@ \subsection{Annotations for External Libraries and Include Files}\label{annotati
 \filename{MyExternalFunctions}\\
 \quad\filename{package.mo}% No line break on last line!
 \end{tabbing}}
+% Adding paragraph break (line break isn't allowed after empty line) below tabbing environment to work around LaTeXML issue:
+% - https://github.com/brucemiller/LaTeXML/issues/1719
+\ifpdf
+\else
+\par
+\fi
 Note that calling the function \lstinline!MyExternalFunctions.ExternalFunc1! will use
 the header and library files from \lstinline!ExternalFunction!, the \lstinline!ExternalFunctions.Example! will not use \filename{ExternalFunc3.c},
 and one library file may contain multiple functions.