- (djm) [bufaux.c compat.c compat.h sshconnect2.c sshd.c version.h]
   OpenSSH 6.5 and 6.6 sometimes encode a value used in the curve25519
   key exchange incorrectly, causing connection failures about 0.2% of
   the time when this method is used against a peer that implements
   the method properly.

   Fix the problem and disable the curve25519 KEX when speaking to
   OpenSSH 6.5 or 6.6. This version will identify itself as 6.6.1
   to enable the compatability code.