Remove usage of getaddrinfo_a() and gai_* functions

The glibc async functions turned out to be unstable and
error-prone. They also use threads to implement timeouts.
If we need DNS timeouts and/or async DNS lookups, we should
have a look at external resolver libraries.

configure.ac

@@ -677,8 +677,6 @@ AS_IF([test "x$with_libmicrohttpd" != xno], [
 ])
 AM_CONDITIONAL([WITH_MICROHTTPD], [test "x$with_libmicrohttpd" = xyes])
 
-AC_SEARCH_LIBS(getaddrinfo_a, anl)
-
 # Check for plugin support
 AC_CANONICAL_HOST
 case "$host_os" in
@@ -733,7 +731,7 @@ AC_CHECK_HEADERS([\
 AC_FUNC_FORK
 AC_FUNC_MMAP
 AC_CHECK_FUNCS([\
- strlcpy getuid fmemopen getaddrinfo_a])
+ strlcpy getuid fmemopen])
 
 AC_CONFIG_FILES([Makefile
                  lib/Makefile

libwget/net.c

@@ -230,69 +230,6 @@ static struct addrinfo *_wget_sort_preferred(struct addrinfo *addrinfo, int pref
 	}
 }
 
-#if defined HAVE_GETADDRINFO_A && ! defined FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
-static int _wget_tcp_resolve(wget_tcp_t *tcp, const char *host, uint16_t port, struct addrinfo **out_addr)
-{
-	int err;
-	char s_port[NI_MAXSERV];
-
-	if (port) {
-		wget_snprintf(s_port, sizeof(s_port), "%hu", port);
-		debug_printf("resolving %s:%s...\n", host ? host : "", s_port);
-	} else {
-		debug_printf("resolving %s...\n", host);
-	}
-
-	struct addrinfo hints = {
-		.ai_family = tcp->family,
-		.ai_socktype = SOCK_STREAM,
-		.ai_flags = AI_ADDRCONFIG | (port ? AI_NUMERICSERV : 0)
-	};
-
-	// shortcut if no timeout has been specified
-	if (tcp->dns_timeout == -1)
-		return getaddrinfo(host, port ? s_port : NULL, &hints, out_addr);
-
-	struct gaicb addr = {
-		.ar_name = host,
-		.ar_service = port ? s_port : NULL,
-		.ar_request = &hints,
-	};
-	struct gaicb *addrs = &addr;
-
-	if ((err = getaddrinfo_a(GAI_NOWAIT, &addrs, 1, NULL))) {
-		debug_printf("getaddrinfo_a() failed (%d): %s\n", err, gai_strerror(err));
-		return err;
-	}
-
-	struct timespec tmo = {
-		.tv_sec = tcp->dns_timeout / 1000,
-		.tv_nsec = (tcp->dns_timeout % 1000) * 1000000
-	};
-
-	if ((err = gai_suspend((const struct gaicb * const *) &addrs, 1, &tmo)) == EAI_AGAIN) {
-		// timeout occurred, do we need to cancel ?
-		int cancel_err = gai_cancel(&addr);
-		debug_printf("gai_cancel = %s\n", gai_strerror(cancel_err));
-	} else if (err == EAI_ALLDONE) {
-		debug_printf("gai_suspend(): %s, accept as OK\n", gai_strerror(err));
-		err = 0;
-	} else if (err)
-		debug_printf("gai_suspend() failed (%d): %s\n", err, gai_strerror(err));
-
-	gai_cancel(NULL); // seems to free some internal memory, but this is not even documented
-
-	if (err == 0) {
-		if (addr.ar_result) {
-			*out_addr = addr.ar_result;
-			addr.ar_result = NULL;
-		} else
-			err = EAI_NODATA; // as returned by getaddrinfo(): "No address associated with hostname"
-	}
-
-	return err;
-}
-#else
 // we can't provide a portable way of respecting a DNS timeout
 static int _wget_tcp_resolve(wget_tcp_t *tcp, const char *host, uint16_t port, struct addrinfo **out_addr)
 {
@@ -313,7 +250,6 @@ static int _wget_tcp_resolve(wget_tcp_t *tcp, const char *host, uint16_t port, s
 		return getaddrinfo(host, NULL, &hints, out_addr);
 	}
 }
-#endif
 
 /**
  * \param[in] tcp A `wget_tcp_t` structure, obtained with a previous call to wget_tcp_init().