Add check for pipe/fifo files

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/fio.h b/fio.h
index 1a31892..7ac5734 100644
--- a/fio.h
+++ b/fio.h
@@ -224,6 +224,7 @@
 	FIO_TYPE_FILE = 1,		/* plain file */
 	FIO_TYPE_BD,			/* block device */
 	FIO_TYPE_CHAR,			/* character device */
+	FIO_TYPE_PIPE,			/* pipe */
 };
 
 enum fio_ioengine_flags {