OpenVPN Release 2.7_rc3

OpenVPN Release 2.7_rc3

version.m4, ChangeLog, Changes.rst

Changes.rst has not received an "2.7_rc3" section - it has the
"highlevel" overview of what is new in 2.7, but for alpha/beta/rc*
releases it's better to look at git log to see what has been added/fixed.

Notable changes rc2 -> rc3 are:
    - Windows/Interactive Service bugfixes
        many small bugfixes to registry-related DNS domain handling
    - Windows/Interactive Service: harden service pipe handling
        close a small race condition, and add restrictive ACLs
    - Windows/Interactive Service: CVE-2025-13751
        fix bug where the interactive service would error-exit in
        certain error conditions instead of just logging the fact and
        continuing.  After the error-exit, OpenVPN connections will no
        longer work until the service is restarted (or the system rebooted).
        This can be triggered by any authenticated local user, and has
        thus been classified as a "local denial of service" attack.
    - more type conversion related warnings have been fixed
    - --multihome behaviour regarding egress interface selection has been
      changed.  See Changes.rst and manpage for details.
    - cleanup dead code in event handling code (leftover of the multisocket
      patch set)
    - add new feature, --tls-crypt-v2-max-age n.  See Changes.rst and
      manpage for details.
    - improve documentation to point out the pitfalls of case-insensitive
      filesystems and --client-config-dir
    - split default gateway query logic in two:
        - for --redirect-gateway functionality, query for the gateway towards
          the actual IP address of the VPN server connecting to
        - for the "net_gateway" special destination for --route, and the
          corresponding environment variable, always query for 0.0.0.0 / ::
      (this will only make a difference in certain scenarios using a local
      proxy, or on a system with multiple interfaces, not using the "default
      route" for the VPN connection - see github#890)
    - upgrade embedded pkcs11-helper vcpkg + pkcs11-uri patch to 1.31
    - CMake / autoconf cleanup wrt unused checks, outdated old-Linux checks,
      Windows oddities
    - DCO (primarily Linux): improve handling of bulk notifications from
      kernel (do not lose notifications, do not crash) (github#900)

Signed-off-by: Gert Doering <gert@greenie.muc.de>