Attempt to clarify what the various IP version selection options do.

[originally from svn r7882]

doc/config.but

@@ -1700,8 +1700,13 @@ TCP keepalives are disabled by default.
 \cfg{winhelp-topic}{connection.ipversion}
 
 This option allows the user to select between the old and new
-Internet protocols and addressing schemes (\i{IPv4} and \i{IPv6}). The
-default setting is \q{Auto}, which means PuTTY will do something
+Internet protocols and addressing schemes (\i{IPv4} and \i{IPv6}).
+The selected protocol will be used for most outgoing network
+connections (including connections to \I{proxy}proxies); however,
+tunnels have their own configuration, for which see
+\k{config-ssh-portfwd-address-family}.
+
+The default setting is \q{Auto}, which means PuTTY will do something
 sensible and try to guess which protocol you wanted. (If you specify
 a literal \i{Internet address}, it will use whichever protocol that
 address implies. If you provide a \i{hostname}, it will see what kinds
@@ -2788,6 +2793,9 @@ incoming connections in both IPv4 and (if available) IPv6
 \b for a remote-to-local port forwarding, PuTTY will choose a
 sensible protocol for the outgoing connection.
 
+This overrides the general Internet protocol version preference
+on the Connection panel (see \k{config-address-family}).
+
 Note that some operating systems may listen for incoming connections
 in IPv4 even if you specifically asked for IPv6, because their IPv4
 and IPv6 protocol stacks are linked together. Apparently \i{Linux} does

doc/using.but

@@ -870,7 +870,8 @@ PuTTY configuration box (see \k{config-ssh-prot}).
 \i{Internet protocol version}
 
 The \c{-4} and \c{-6} options force PuTTY to use the older Internet
-protocol \i{IPv4} or the newer \i{IPv6}.
+protocol \i{IPv4} or the newer \i{IPv6} for most outgoing
+connections.
 
 These options are equivalent to selecting your preferred Internet
 protocol version as \q{IPv4} or \q{IPv6} in the Connection panel of