Add index entry "I/O control, buffering" for makefile().
diff --git a/Doc/lib/libsocket.tex b/Doc/lib/libsocket.tex
index 64a659a..2639f4e 100644
--- a/Doc/lib/libsocket.tex
+++ b/Doc/lib/libsocket.tex
@@ -199,7 +199,7 @@
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 @@
\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}