Auto-sync with upstream branch master
    
    Upstream commit: 3556658c5b8765480711b265abc901c67d5fc060
    
    - Regenerate po/libc.pot for 2.30 release.
    - nptl: Add POSIX-proposed _clock functions to hppa pthread.h
    - nptl: Remove unnecessary forwarding of pthread_cond_clockwait from libc
    - Afar locales: Months and days updated from CLDR (bug 21897).
    - nl_BE locale: Use "copy "nl_NL"" in LC_NAME (bug 23996).
    - nl_BE and nl_NL locales: Dutch salutations (bug 23996).
    - ga_IE and en_IE locales: Revert first_weekday removal (bug 24200).
    - nptl: Remove futex_supports_exact_relative_timeouts
    - Update NEWS for new _clockwait and _clocklock functions
    - nptl: Add POSIX-proposed pthread_mutex_clocklock
    - nptl: Rename lll_timedlock to lll_clocklock and add clockid parameter
    - nptl: Add POSIX-proposed pthread_rwlock_clockrdlock & pthread_rwlock_clockwrlock
    - nptl: pthread_rwlock: Move timeout validation into _full functions
    - nptl: Add POSIX-proposed pthread_cond_clockwait
    - nptl: Add POSIX-proposed sem_clockwait
    - nptl: Add clockid parameter to futex timed wait calls
    - posix: Fix large mmap64 offset for mips64n32 (BZ#24699)
    - nss_db: fix endent wrt NULL mappings [BZ #24695] [BZ #24696]