PUSH_UPDATE: Added update_option() function.

PUSH_UPDATE: Added update_option() function.

When the function receives an option to update, it first checks whether it has
already received an option of the same type within the same update message.
If it has already received it, it simply calls add_option(), otherwise it
deletes all the values already present for that option first.

Change-Id: Ia45c99e6df7b3ad24020c10b8a9b3577984ecdc2
Signed-off-by: Marco Baffo <marco@mandelbit.com>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20250729104110.27704-1-gert@greenie.muc.de>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg32408.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>