Depreciation warning for --topology net30 on servers with IPv4 pools.

Depreciation warning for --topology net30 on servers with IPv4 pools.

IPv4 pool handling needs lots of extra code to deal with "topology net30",
so we want to remove that combination in a future release.

Warn people about this in 2.5 so nobody is hit by this as a surprise.

Client- and ifconfig-support for net30 will stay, as "just net30" is not
what brings maintenance effort here (totally removing all options except
"topology subnet" would be beneficial but is a bit too radical today)

Trac: #1288

Signed-off-by: Gert Doering <gert@greenie.muc.de>
Acked-by: Arne Schwabe <arne@rfc2549.org>
Message-Id: <20200620180532.15738-1-gert@greenie.muc.de>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg20041.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>