Log Message:
net/syncthing: Update to 1.8.0

While there is 1.9.0, it is only two days old and isn't in f-droid
yet.  I am choosing to avoid new releases for a bit, on the theory
that it's better to let people other than pkgsrc users find any new
issues.

Tested with syncthing Android/f-droid 1.8.0.

Upstream changes:

    bugfixes and minor enhanceements

    adds the experimental copyRangeMethod config on folders, for use
    on filesystems with copy-on-write support. Please see
    https://docs.syncthing.net/advanced/folder-copyrangemethod.html
    for details.

    adds TCP hole punching, used to establish high performance TCP
    connections in certain NAT scenarios where only relay or QUIC
    connections could be used previously.

    adds a configuration to file versioning for how often to run
    cleanup.  This defaults to once an hour, but is configurable from
    very frequently to never.