Second definition of popen2 should be popen3.

Doc/lib/libpopen2.tex

@@ -23,7 +23,7 @@ it specifies the buffer size for the I/O pipes.  Returns
 \code{(\var{child_stdout}, \var{child_stdin})}.
 \end{funcdesc}
 
-\begin{funcdesc}{popen2}{cmd\optional{, bufsize}}
+\begin{funcdesc}{popen3}{cmd\optional{, bufsize}}
 Executes \var{cmd} as a sub-process.  If \var{bufsize} is specified, 
 it specifies the buffer size for the I/O pipes.  Returns
 \code{(\var{child_stdout}, \var{child_stdin}, \var{child_stderr})}.