Add support for dynamically adjusted buffers to allow the full use of
the bandwidth of long fat pipes (i.e. 100Mbps+ trans-oceanic or
trans-continental links). Bandwidth-delay products up to 64MB are
supported.

Also add support (not compiled by default) for the None cypher. The
None cypher can only be enabled on non-interactive sessions (those
without a pty where -T was not used) and must be enabled in both
the client and server configuration files and on the client command
line. Additionally, the None cypher will only be activated after
authentication is complete. To enable the None cypher you must add
-DNONE_CIPHER_ENABLED to CFLAGS via the make command line or in
/etc/make.conf.

This code is a style(9) compliant version of these features extracted
from the patches published at:

http://www.psc.edu/networking/projects/hpn-ssh/

Merging this patch has been a collaboration between me and Bjoern.

Reviewed by: bz
Approved by: re (kib), des (maintainer)