net/libpfctl: support FreeBSD 12 and 13

Extend the port to also build for FreeBSD 12.4 and FreeBSD 13.1.
While here also update the 14.0 hash to a more recent code snapshot.

Reviewed by: garga
Sponsored by: Rubicon Communications, LLC ("Netgate")
Differential Revision: https://reviews.freebsd.org/D39360