Add null declaration of AI_NUMERICINFO.

Some platforms (older FreeBSD and DragonFly versions) do have
getaddrinfo() but do not have AI_NUMERICINFO. so define it to zero
in those cases.
diff --git a/configure.ac b/configure.ac
index cb66f54..2ef9db6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2197,6 +2197,13 @@
 	)
 fi
 
+if test "x$ac_cv_func_getaddrinfo" = "xyes"; then
+	AC_CHECK_DECLS(AI_NUMERICSERV, , ,
+	    [#include <sys/types.h>
+	     #include <sys/socket.h>
+	     #include <netdb.h>])
+fi
+
 if test "x$check_for_conflicting_getspnam" = "x1"; then
 	AC_MSG_CHECKING([for conflicting getspnam in shadow.h])
 	AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[ #include <shadow.h> ]],
diff --git a/defines.h b/defines.h
index f489196..1ec9467 100644
--- a/defines.h
+++ b/defines.h
@@ -594,6 +594,10 @@
 # undef HAVE_GAI_STRERROR
 #endif
 
+#if defined(HAVE_GETADDRINFO) && !defined(HAVE_DECL_AI_NUMERICSERV)
+# define AI_NUMERICSERV	0
+#endif
+
 #if defined(BROKEN_UPDWTMPX) && defined(HAVE_UPDWTMPX)
 # undef HAVE_UPDWTMPX
 #endif