Auto-sync with upstream branch master
    
    Upstream commit: d05e6dc8d1032e1732542a48e0fb895432008b6e
    
    - hppa: Implement swapcontext in assembler (bug 28960)
    - associate a deallocator for iconv_open
    - associate a deallocation for opendir
    - Add access function attributes to epoll_wait
    - Add access function attributes to grp and shadow headers
    - Define ISO 639-3 "tok" [BZ #28950]
    - nss: Protect against errno changes in function lookup (bug 28953)
    - nss: Do not mention NSS test modules in <gnu/lib-names.h>
    - malloc: Exit early on test failure in tst-realloc
    - Add some missing access function attributes
    - libio: Ensure output buffer for wchars (bug #28828)
    - inet: Return EAI_MEMORY when nrl_domainname() fails to allocate memory
    - inet: Remove strdupa from nrl_domainname()
    - inet: Fix getnameinfo (NI_NOFQDN) race condition (BZ#28566)
    - benchtests: make compare_strings.py accept string as attribute value