Auto-sync with upstream branch master
    
    Upstream commit: d34d4c80226b3f5a1b51a8e5b005a52fba07d7ba
    
    - Merge upstream nsswitch.conf and nscd.conf updates.
    - Do not print backtraces on fatal glibc errors.
    - elf: Self-dlopen failure with explict loader invocation (swbz#24900)
    - login: Add nonstring attributes to struct utmp, struct utmpx (swbz#24899)
    - login: Use struct flock64 in utmp (swbz#24880)
    - login: Disarm timer after utmp lock acquisition (swbz#24879)