gnutls: Update to 3.6.7.1

gnutls: Update to 3.6.7.1

For details see:
https://lists.gnupg.org/pipermail/gnutls-help/2019-March/004497.html

Please note:
A few days after the "3.6.7" release, "3.6.7.1" came out.

See:
https://www.gnupg.org/ftp/gcrypt/gnutls/v3.6/

But the compressed directory version is still versioned 3.6.7.

Because of this, the fourth (sub)-version number required some lfs adjustments.

And:
This version requires "nettle 3.4.1", which is sent in another commit.

Signed-off-by: Matthias Fischer <matthias.fischer@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>