Add ATT, attribute macros.
Fix return value of uio_copy.
Add uio_null() to create "NULL" UIO stream.
Add uio_find.
Add top function to SS. Add missing static.
Touch up SS documentation.
Improve SCRATCH API.

- Remove flush_left (made static).
- Add full and clear.
Make TF output prettier in compilation buffer.
Add initial implementation of FORTY.