add references between getopt and optparse docs

Doc/lib/libgetopt.tex

@@ -143,3 +143,7 @@ def main():
 if __name__ == "__main__":
     main()
 \end{verbatim}
+
+\begin{seealso}
+  \seemodule{optparse}{More object-oriented command line option parsing}
+\end{seealso}

Doc/lib/liboptparse.tex

@@ -1709,3 +1709,7 @@ attribute; extend \class{OptionParser} to ensure that required options
 are present after parsing:
 
 \verbatiminput{required_2.py}
+
+\begin{seealso}
+  \seemodule{getopt}{More traditional Unix-style command line option parsing}
+\end{seealso}