many warnings compile with clang

[leleliu008]

/tmp/tmp.F4CPONhvAn/dns/dns.c:303:5: warning: macro expansion producing 'defined' has undefined behavior [-Wexpansion-to-defined]
#if HAVE___ATOMIC_FETCH_ADD && __GCC_ATOMIC_LONG_LOCK_FREE == 2
    ^
/tmp/tmp.F4CPONhvAn/dns/dns.c:295:34: note: expanded from macro 'HAVE___ATOMIC_FETCH_ADD'
#define HAVE___ATOMIC_FETCH_ADD (defined __ATOMIC_RELAXED)
                                 ^
/tmp/tmp.F4CPONhvAn/dns/dns.c:312:5: warning: macro expansion producing 'defined' has undefined behavior [-Wexpansion-to-defined]
#if HAVE___ATOMIC_FETCH_SUB && __GCC_ATOMIC_LONG_LOCK_FREE == 2
    ^
/tmp/tmp.F4CPONhvAn/dns/dns.c:299:33: note: expanded from macro 'HAVE___ATOMIC_FETCH_SUB'
#define HAVE___ATOMIC_FETCH_SUB HAVE___ATOMIC_FETCH_ADD
                                ^
/tmp/tmp.F4CPONhvAn/dns/dns.c:295:34: note: expanded from macro 'HAVE___ATOMIC_FETCH_ADD'
#define HAVE___ATOMIC_FETCH_ADD (defined __ATOMIC_RELAXED)
                                 ^
/tmp/tmp.F4CPONhvAn/dns/dns.c:668:5: warning: macro expansion producing 'defined' has undefined behavior [-Wexpansion-to-defined]
#if DNS_HAVE_SOCKADDR_UN
    ^
/tmp/tmp.F4CPONhvAn/dns/dns.c:662:31: note: expanded from macro 'DNS_HAVE_SOCKADDR_UN'
#define DNS_HAVE_SOCKADDR_UN (defined AF_UNIX && !defined _WIN32)
                              ^
/tmp/tmp.F4CPONhvAn/dns/dns.c:668:5: warning: macro expansion producing 'defined' has undefined behavior [-Wexpansion-to-defined]
/tmp/tmp.F4CPONhvAn/dns/dns.c:662:51: note: expanded from macro 'DNS_HAVE_SOCKADDR_UN'
#define DNS_HAVE_SOCKADDR_UN (defined AF_UNIX && !defined _WIN32)
                                                  ^
/tmp/tmp.F4CPONhvAn/dns/dns.c:723:5: warning: macro expansion producing 'defined' has undefined behavior [-Wexpansion-to-defined]
#if DNS_HAVE_SOCKADDR_UN
    ^
/tmp/tmp.F4CPONhvAn/dns/dns.c:662:31: note: expanded from macro 'DNS_HAVE_SOCKADDR_UN'
#define DNS_HAVE_SOCKADDR_UN (defined AF_UNIX && !defined _WIN32)
                              ^
/tmp/tmp.F4CPONhvAn/dns/dns.c:723:5: warning: macro expansion producing 'defined' has undefined behavior [-Wexpansion-to-defined]
/tmp/tmp.F4CPONhvAn/dns/dns.c:662:51: note: expanded from macro 'DNS_HAVE_SOCKADDR_UN'
#define DNS_HAVE_SOCKADDR_UN (defined AF_UNIX && !defined _WIN32)
                                                  ^
/tmp/tmp.F4CPONhvAn/dns/dns.c:729:5: warning: macro expansion producing 'defined' has undefined behavior [-Wexpansion-to-defined]
#if DNS_HAVE_SOCKADDR_UN
    ^
/tmp/tmp.F4CPONhvAn/dns/dns.c:662:31: note: expanded from macro 'DNS_HAVE_SOCKADDR_UN'
#define DNS_HAVE_SOCKADDR_UN (defined AF_UNIX && !defined _WIN32)
                              ^
/tmp/tmp.F4CPONhvAn/dns/dns.c:729:5: warning: macro expansion producing 'defined' has undefined behavior [-Wexpansion-to-defined]
/tmp/tmp.F4CPONhvAn/dns/dns.c:662:51: note: expanded from macro 'DNS_HAVE_SOCKADDR_UN'
#define DNS_HAVE_SOCKADDR_UN (defined AF_UNIX && !defined _WIN32)
                                                  ^
/tmp/tmp.F4CPONhvAn/dns/dns.c:789:5: warning: macro expansion producing 'defined' has undefined behavior [-Wexpansion-to-defined]
#if DNS_HAVE_SOCKADDR_UN
    ^
/tmp/tmp.F4CPONhvAn/dns/dns.c:662:31: note: expanded from macro 'DNS_HAVE_SOCKADDR_UN'
#define DNS_HAVE_SOCKADDR_UN (defined AF_UNIX && !defined _WIN32)
                              ^
/tmp/tmp.F4CPONhvAn/dns/dns.c:789:5: warning: macro expansion producing 'defined' has undefined behavior [-Wexpansion-to-defined]
/tmp/tmp.F4CPONhvAn/dns/dns.c:662:51: note: expanded from macro 'DNS_HAVE_SOCKADDR_UN'
#define DNS_HAVE_SOCKADDR_UN (defined AF_UNIX && !defined _WIN32)
                                                  ^
10 warnings generated.