Auto-sync with upstream branch release/2.26/master
    
    Upstream commit: a0bc5dd3bed4b04814047265b3bcead7ab973b87
    
    - CVE-2018-19591: if_nametoindex: Fix descriptor leak (#1654000)
    - libanl: proper cleanup if first helper thread creation failed (#1646381)
    - x86: Fix Haswell CPU string flags (#1641980)
    - resolv/tst-resolv-network.c: Additional test case (swbz#17630)
    - Disable -Wrestrict for two nptl/tst-attr3.c tests
    - Fix string/bug-strncat1.c build with GCC 8
    - Ignore -Wrestrict for one strncat test
    - Disable strncat test array-bounds warnings for GCC 8.
    - Fix string/tester.c build with GCC 8.
    - Fix nscd readlink argument aliasing (swbz#22446)
    - nscd: Increase buffer size due to warning from ToT GCC
    - Fix p_secstodate overflow handling (swbz#22463)
    - timezone: pacify GCC -Wstringop-truncation
    - utmp: Avoid -Wstringop-truncation warning
    - Avoid use of strlen in getlogin_r (swbz#22447)
    - signal: Use correct type for si_band in siginfo_t (swbz#23562)
    - Fix misreported errno on preadv2/pwritev2 (swbz#23579)
    - preadv2/pwritev2: Handle offset == -1 (swbz#22753)
    - posix_spawn: Fix potential segmentation fault