security/vuxml: add FreeBSD SAs issued on 2026-07-29

FreeBSD-SA-26:50.kqueue affects 15.1R
FreeBSD-SA-26:51.ktimer affects 15.0R and 15.1R
FreeBSD-SA-26:52.if_wg affects all supported releases
FreeBSD-SA-26:53.ktrace affects 15.0R and 15.1R
FreeBSD-SA-26:54.sysvsem affects all supported releases
FreeBSD-SA-26:55.elf affects all supported releases