BUG/MINOR: build: Fix compilation with debug mode enabled

It remained some fragments of the old buffers API in debug messages, here and
there.

This was caused by the recent buffer API changes, no backport is needed.
diff --git a/src/cli.c b/src/cli.c
index 0d3c95c..d028429 100644
--- a/src/cli.c
+++ b/src/cli.c
@@ -764,9 +764,9 @@
 	}
 
  out:
-	DPRINTF(stderr, "%s@%d: st=%d, rqf=%x, rpf=%x, rqh=%d, rqs=%d, rh=%d, rs=%d\n",
+	DPRINTF(stderr, "%s@%d: st=%d, rqf=%x, rpf=%x, rqh=%lu, rqs=%lu, rh=%lu, rs=%lu\n",
 		__FUNCTION__, __LINE__,
-		si->state, req->flags, res->flags, req->buf->i, req->buf->o, res->buf->i, res->buf->o);
+		si->state, req->flags, res->flags, ci_data(req), co_data(req), ci_data(res), co_data(res));
 }
 
 /* This is called when the stream interface is closed. For instance, upon an