Include <arpa/nameser.h> before <resolv.h>.

diff --git a/configure.ac b/configure.ac
index 289b3f7..2312127 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1093,6 +1093,9 @@
      #endif
      #if HAVE_NETINET_IN_H
      # include <netinet/in.h>
+     #endif
+     #if HAVE_ARPA_NAMESER_H
+     # include <arpa/nameser.h>
      #endif])
 
 AC_CHECK_HEADERS(netinet/ip.h,,,