Fix markup errors.

Doc/lib/libposixpath.tex

@@ -216,7 +216,7 @@ avoid visiting certain parts of the tree.  (The object referred to by
 assignment.)
 
 Note that symbolic links to directories are not treated as subdirectories,
-and that \var{walk} therefore will not visit them. To visit linked
-directories you must identify them with \var{os.path.islink(file)} and
-\var{os.path.isdir(file)}, and invoke \function{walk()} as necessary.
+and that \function{walk} therefore will not visit them. To visit linked
+directories you must identify them with \code{os.path.islink(file)} and
+\code{os.path.isdir(file)}, and invoke \function{walk()} as necessary.
 \end{funcdesc}