libssh2 1.2.6

This release includes the following changes:

 o Added libssh2_sftp_statvfs() and libssh2_sftp_fstatvfs()
 o Added libssh2_knownhost_checkp()
 o Added libssh2_scp_send64()

This release includes the following bugfixes:

 o wait_socket: make c89 compliant and use two fd_sets for select()
 o OpenSSL AES-128-CTR detection
 o proper keyboard-interactive user dialog in the sftp.c example
 o build procedure for VMS
 o fixed libssh2.dsw to use the generated libssh2.dsp
 o several Windows-related build fixes
 o fail to init SFTP if session isn't already authenticated
 o many tiny fixes that address clang-analyzer warnings
 o sftp_open: deal with short channel_write calls
 o libssh2_publickey_init: fixed to work better non-blocking
 o sftp_close_handle: add precation to not access NULL pointer
 o sftp_readdir: simplified and bugfixed
 o channel_write: if data has been sent, don't return EAGAIN

This release would not have looked like this without help, code, reports and
advice from friends like these:

 Alexander Lamaison, Guenter Knauf, Dan Fandrich, Grubsky Grigory,
 Joey Degges, Jose Baars, Mikhail Gusarov, Peter Stuge, Simon Josefsson,
 Daniel Stenberg
 
        Thanks! (and sorry if I forgot to mention someone)
