security/openvpn-devel: upgrade port to git commit 4281449ba4 (2.7_rc1, 2025-10-31)

This commit brings the port to "openvpn 2.7_rc1".

Changes of interest for FreeBSD:

• even more type conversion related warnings have been fixed
• more bugfixes related to BYTECOUNT display on the management interface and byte counters on DCO platforms in general
• numerous minibugs reported by ZeroPath AI have been fixed (small memleaks, possible file descriptor leaks, improved sanity checks, add ASSERT() on function contracts, etc.)
• add warning for unsupported combination of --push and --tls-server
• add warning for unsupported combination of --reneg-bytes or --reneg-pkts with DCO
• remove perf_push()/perf_pop() infrastructure (because it did not work anymore, and compiler profiling will give better results today)
• ensure compatibility with OpenSSL 3.6.0 - specifically, do not crash in t_lpback.sh trying to use new encrypt-then-mac (ETM) ciphers
• improved PUSH_UPDATE server side support, which now handles changes of pushed ifconfig/ifconfig-ipv6 addresses correctly (send packets to new IP addresses to this client, stop sending packets to the old addresses).
• bugfixes reconnect and PUSH_UPDATE handling on the client side (notably handling of ifconfig/ifconfig-ipv6/redirect-gateway ipv6 if the server is not always pushing the same address families)
• improve CONTRIBUTING documentation
• clean up and remove outdated stuff from COPYING
• freshen URLs all over the tree, and change to HTTPS where possible
• on DCO Linux/FreeBSD, add support for clients receiving an IPv4/IPv6 address that is not part of the --server/--server-ipv6 subnet (= install extra on-interface host routes).
• remove undocumented and unused --memstats feature
• improve "recursive routing checks", prepare the way for a policy-based setup where "packets to VPN server" could end up in the tunnel without interfering with OpenVPN operations

(cherry picked from commit e4baec8206e849270394a508040cbcaa6d9275d4)

PR: 290715