configure: fix check for libnsl

Pointed-out-by: Jon Tibble <meths@btinternet.com>

configure.ac

@@ -592,7 +592,7 @@ AC_SEARCH_LIBS(connect, [socket], [
   ])
 ])
 
-AC_SEARCH_LIBS([getaddrinfo], [nsl], [
+AC_SEARCH_LIBS([inet_pton], [nsl], [
  AS_IF([test "$ac_cv_search_getaddrinfo" != "none required"], [
     SOCKET_LIBS="$ac_cv_search_getaddrinfo $SOCKET_LIBS"
   ])