g10/decrypt-data: disable output estream buffering to reduce overhead

* g10/decrypt-data.c (decrypt_data): Disable estream buffering for
output file.
--

Here estream is filled with iobuf_copy which already uses large buffers
so additional buffering in estream was just adding memory copy overhead.

GnuPG-bug-id: T5828
Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>

g10/decrypt-data.c

@@ -484,6 +484,8 @@ decrypt_data (ctrl_t ctrl, void *procctx, PKT_encrypted *ed, DEK *dek)
           iobuf_t output = iobuf_esopen (fp, "w", 0, 0);
           armor_filter_context_t *afx = NULL;
 
+	  es_setbuf (fp, NULL);
+
           if (opt.armor)
             {
               afx = new_armor_context ();