Ooops - for some reason I had the wrong versionadded...

Doc/lib/libsocket.tex

@@ -308,7 +308,7 @@ Build a pair of connected socket objects using the given address
 family, socket type and protocol number.  Address family, socket type
 and protocol number are as for the \function{socket()} function above.
 Availability: \UNIX.
-\versionadded{2.3}
+\versionadded{2.4}
 \end{funcdesc}
 
 \begin{funcdesc}{fromfd}{fd, family, type\optional{, proto}}