Fix various security vulnerabilities in glibc-2.44

[Xi Ruoyao]

There are some security vulnerabilities fixed after glibc-2.44:

advisories/GLIBC-SA-2026-0015:CVE-Id: CVE-2026-18374
advisories/GLIBC-SA-2026-0017:CVE-Id: CVE-2026-19499
advisories/GLIBC-SA-2026-0018:CVE-Id: CVE-2026-19542
advisories/GLIBC-SA-2026-0019:CVE-Id: CVE-2026-77117
advisories/GLIBC-SA-2026-0020:CVE-Id: CVE-2026-80489
advisories/GLIBC-SA-2026-0021:CVE-Id: CVE-2026-8674

GLIBC-SA-2026-0014 and earlier are already fixed in 2.44. GLIBC-SA-2026-0016 is for nscd that we've disabled already.

I have doubts about some of them (at least, CVE-2026-18374 seems just a normal bug with almost no security implication to me) but let's fix them anyway. As the current upstream fixes patch is a bulk one containing everything (at that moment) on the glibc-2.44 maintenance branch, I'll just export a new patch containing everything on the branch as at now as well.