CLSA-2021-1635459187 Fix CVE(s): CVE-2021-33574, CVE-2021-38604, CVE-2021-35942

debian/patches/any/add-pthread-attr-copy.patch: adopt pthreadattrcopy functionality. debian/patches/any/add-test-for-pthread-attr-copy.patch: add test case for it. SECURITY UPDATE: Use-after-free in mqnotify - debian/patches/any/CVE-2021-33574.patch: use pthreadattrcopy to completely duplicate...