Ssh

-----------------------
* added support for "old" group-exchange server mode, for compatibility
with the windows putty client
* fixed some more interactions with SFTP file readv() and prefetch()
* when saving the known_hosts file, preserve the original order [patch from
warren young]
* fix a couple of broken lines when exporting classes (bug 55946)

-----------------------
* more unit tests fixed for windows/cygwin (thanks to alexander belchenko)
* a couple of fixes related to exceptions leaking out of SFTPClient
* added ability to set items in HostKeys via __setitem__
* HostKeys now retains order and has a save() method
* added PKey.write_private_key and PKey.from_private_key

----------------------
* pageant support on Windows thanks to john arbash meinel and todd whiteman
* fixed unit tests to work under windows and cygwin (thanks to alexander
belchenko for debugging)
* various bugfixes/tweaks to SFTP file prefetch
* added SSHClient for a higher-level API
* SFTP readv() now yields results as it gets them
* several APIs changed to throw an exception instead of "False" on failure

--------------------------
* fixed HostKeys to more correctly emulate a python dict
* fixed a bug where file read buffering was too aggressive
* improved prefetching so that out-of-order reads still use the prefetch
buffer
* added experimental SFTPFile.readv() call
* more unit tests

-------------------------
* a few performance enhancements
* added HostKeys, for dealing with openssh style "known_hosts" files, and
added support for hashed hostnames
* added Transport.atfork() for dealing with forked children
* added SFTPClient.truncate, SFTPFile.chmod, SFTPFile.chown, SFTPFile.utime,
and SFTPFile.truncate
* improved windows demos [patch from mike looijmans], added an sftp demo, and
moved demos to the demos/ folder
* fixed a few interoperability bugs
* cleaned up logging a bit
* fixed a bug where EOF on a Channel might not be detected by select [found
by thomas steinacher]
* fixed python 2.4-ism that crept in [patch by jan hudec]
* fixed a few reference loops that could have interacted badly with the python
garbage collector
* fixed a bunch of pychecker warnings, some of which were bugs

-----------------------
* compression support (opt-in via Transport.use_compression)
* sftp files may be opened with mode flag 'x' for O_EXCL (exclusive-open)
behavior, which has no direct python equivalent
* added experimental util functions for parsing openssh config files
* fixed a few bugs (and potential deadlocks) with key renegotiation
* fixed a bug that caused SFTPFile.prefetch to occasionally lock up
* fixed an sftp bug which affected van dyke sftp servers
* fixed the behavior of select()ing on a closed channel, such that it will
always trigger as readable