Increase the BUFSIZ-long buffers

The BUFSIZ value varies between platforms, it could be 8K on Linux and
512 bytes on mingw.  Make sure the buffers are always big enough for the
output data to prevent truncation of the output by appropriately
enlarging or sizing the buffers.

lib/ns/client.c

@@ -12,6 +12,7 @@
  */
 
 #include <inttypes.h>
+#include <limits.h>
 #include <stdbool.h>
 
 #include <isc/aes.h>
@@ -955,7 +956,7 @@ isc_result_t
 ns_client_addopt(ns_client_t *client, dns_message_t *message,
 		 dns_rdataset_t **opt) {
 	unsigned char ecs[ECS_SIZE];
-	char nsid[BUFSIZ], *nsidp = NULL;
+	char nsid[_POSIX_HOST_NAME_MAX + 1], *nsidp = NULL;
 	unsigned char cookie[COOKIE_SIZE];
 	isc_result_t result;
 	dns_view_t *view = NULL;