Auto-sync with upstream branch release/2.27/master
    
    Upstream commit: 9f433fc791ca4f9d678903ff45b504b524c886fb
    
    - 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)
    - ia64: fix missing exp2f, log2f and powf symbols in libm.a (swbz#23822)
    - conform: XFAIL siginfo_t si_band test on sparc64
    - signal: Use correct type for si_band in siginfo_t (swbz#23562)
    - pthread_mutex_lock: Fix race while promoting to PTHREAD_MUTEX_ELISION_NP
      (swbz#23275)
    - preadv2/pwritev2: Fix misreported errno (swbz#23579)
    - preadv2/pwritev2: Handle offset == -1 (swbz#22753)
    - posix_spawn: Fix potential segmentation fault