net-mgmt/lldpd: Update to 1.0.18

- Use writable chroot for timezone file
- USES=pkgconfig to detect system libevent
- Remove obsolete (since 0.9.7) JSON option
- Remove unnecessary USES=libedit with XML option
- Pet portlint and other minor improvements

Changelogs:
- https://github.com/lldpd/lldpd/releases/tag/1.0.15
- https://github.com/lldpd/lldpd/releases/tag/1.0.16
- https://github.com/lldpd/lldpd/releases/tag/1.0.17
- https://github.com/lldpd/lldpd/releases/tag/1.0.18

PR: 277851
Reported by: ngie
Reviewed by: ngie
Approved by: maintainer timeout (three months)
Sponsored by: Saltant Solutions LLC
Differential Revision: https://reviews.freebsd.org/D45168