some issues regarding OFB and CFB mode

Hi,

I found some missing features in the current implementation of pycrypto:

1.
The modes OFB and CFB should work as real stream ciphers. There
is no need to depend on the BLOCKSIZE or the segment_size.

2.
The OFB mode should work with different segement_sizes (and not only
with the blocksize).

Is there a reason why the current implementation doesn't implement these
features?

Nevertheless I've made a patch to allow the OFB mode to work as a real stream
cipher so you can encrypt strings with every length.

https://sourceforge.net/tracker/index.php?func=detail&aid=626587&group_id=20937&atid=320937

If I have time, I'll create the according patch for CFB and for 2.

regards,
christian