Auto-sync with upstream release/2.26/master
    
    Upstream commit: a71a3374cd8cf53776c33994f69ec184c26f2129
    
    - Provide a C++ version of issignaling that does not use __MATH_TG
    - Provide a C++ version of iszero that does not use __MATH_TG (swbz#21930)
    - getaddrinfo: Return EAI_NODATA if gethostbyname2_r with NO_DATA (swzbz#21922)
    - getaddrinfo: Fix error handling in gethosts (swbz#21915)