Add versionadded for has_ipv6 attribute
diff --git a/Doc/lib/libsocket.tex b/Doc/lib/libsocket.tex
index 73c0ff3..6b86eea 100644
--- a/Doc/lib/libsocket.tex
+++ b/Doc/lib/libsocket.tex
@@ -153,6 +153,7 @@
 \begin{datadesc}{has_ipv6}
 This constant contains a boolean value which indicates if IPv6 is
 supported on this platform.
+\versionadded{2.3}
 \end{datadesc}
 
 \begin{funcdesc}{getaddrinfo}{host, port\optional{, family, socktype, proto, flags}}