Added link to xdrlib module in "See also" section.

Doc/lib/libstruct.tex

@@ -169,5 +169,6 @@ This only works when native size and alignment are in effect;
 standard size and alignment does not enforce any alignment.
 
 \begin{seealso}
-\seemodule{array}{packed binary storage of homogeneous data}
+  \seemodule{array}{packed binary storage of homogeneous data}
+  \seemodule{xdrlib}{packing and unpacking of XDR data}
 \end{seealso}