Add index entry "I/O control, buffering" for makefile().

Doc/lib/libsocket.tex

@@ -199,7 +199,7 @@ This is a Python type object that represents the socket object type.
 It is the same as \code{type(socket(...))}.
 \end{datadesc}
 
-\subsection{Socket Objects}
+\subsection{Socket Objects \label{socket-objects}}
 
 Socket objects have the following methods.  Except for
 \method{makefile()} these correspond to \UNIX{} system calls
@@ -279,10 +279,11 @@ least 1; the maximum value is system-dependent (usually 5).
 
 \begin{methoddesc}[socket]{makefile}{\optional{mode\optional{, bufsize}}}
 Return a \dfn{file object} associated with the socket.  (File objects
-were described earlier in \ref{bltin-file-objects}, ``File Objects.'')
+are described in \ref{bltin-file-objects}, ``File Objects.'')
 The file object references a \cfunction{dup()}ped version of the
 socket file descriptor, so the file object and socket object may be
-closed or garbage-collected independently.  The optional \var{mode}
+closed or garbage-collected independently.
+\index{I/O control!buffering}The optional \var{mode}
 and \var{bufsize} arguments are interpreted the same way as by the
 built-in \function{open()} function.
 \end{methoddesc}