- build package on platforms other than NetBSD

  PFKEYV2 and XFRM are pretty esoteric.

  Libreswan builds on Fedora, Debian, Alpine (they each have their own
  packaing quirks), FreeBSD, NetBSD, OpenBSD.

- add following entries to pkg-vulnerabilities

libreswan<5.3.2		denial-of-service	https://libreswan.org/security/CVE-2026-14957/CVE-2026-14957.txt
libreswan<5.3.1		denial-of-service	https://libreswan.org/security/CVE-2026-12413/CVE-2026-12413.txt
libreswan<5.3.1		denial-of-service	https://libreswan.org/security/CVE-2026-50721/CVE-2026-50721.txt
libreswan<5.3.1		denial-of-service	https://libreswan.org/security/CVE-2026-50722/CVE-2026-50722.txt

libreswan<5.0rc3	denial-of-service	https://libreswan.org/security/CVE-2024-3652/CVE-2024-3652.txt
libreswan<5.0rc2	denial-of-service	https://libreswan.org/security/CVE-2024-2357/CVE-2024-2357.txt

libreswan<4.15		denial-of-service	https://libreswan.org/security/CVE-2024-3652/CVE-2024-3652.txt
libreswan<4.13nb1	denial-of-service	https://libreswan.org/security/CVE-2024-2357/CVE-2024-2357.txt
libreswan<4.12nb1	denial-of-service	https://libreswan.org/security/CVE-2023-38712/CVE-2023-38712.txt
libreswan<4.12nb1	denial-of-service	https://libreswan.org/security/CVE-2023-38711/CVE-2023-38711.txt
libreswan<4.12nb1	denial-of-service	https://libreswan.org/security/CVE-2023-38710/CVE-2023-38710.txt
libreswan<4.9nb3	denial-of-service	https://libreswan.org/security/CVE-2023-30570/CVE-2023-30570.txt
libreswan<4.9nb2	denial-of-service	https://libreswan.org/security/CVE-2023-23009/CVE-2023-23009.txt
libreswan<4.6		denial-of-service	https://libreswan.org/security/CVE-2022-23094/CVE-2022-23094.txt

Notes:

4.7		earliest pkgsrc version, 4.6 is just a baseline
CVE-2023-2295	was a bug in Red Hat's Libreswan package, not Libreswan
4.9nb2 4.9nb3	were cut from libreswan's mainline
