ldns: Upgrade to 1.8.3.
Merge commit 'cf3e3d5bd0a1fae39c74c7db5a4e8b10732d0766'
Reviewed by: emaste
Differential Revision: https://reviews.freebsd.org/D40226
(cherry picked from commit 5afab0e5e56fe90a378fb57249600e7924e1cab2)
ldns: Remove a set but unused variable.
Reviewed by: des
Differential Revision: https://reviews.freebsd.org/D40695
(cherry picked from commit 2e1665ff345498c3f99ffd07b6e90669172d2df2)