security/vuxml: add FreeBSD SAs issued on 2026-04-29

FreeBSD-SA-26:12.dhclient affects all supported releases
FreeBSD-SA-26:13.exec affects all supported releases
FreeBSD-SA-26:14.pf affects all supported releases
FreeBSD-SA-26:15.dhclient affects all supported releases
FreeBSD-SA-26:16.libnv affects all supported releases
FreeBSD-SA-26:17.libnv affects all supported releases