lib/standard/streams: Added simple error management for streams

Signed-off-by: Lucas Bajolet <r4pass@hotmail.com>
lib/standard: Got rid of FDStream, reified under FStream

Signed-off-by: Lucas Bajolet <r4pass@hotmail.com>
lib/standard/file: Auto-flush write streams

Signed-off-by: Lucas Bajolet <r4pass@hotmail.com>