Log Message:
Update openssh to 6.4.1 (OpenSSH 6.4p1).

Changes since OpenSSH 6.3
=========================

This release fixes a security bug:

 * sshd(8): fix a memory corruption problem triggered during rekeying
   when an AES-GCM cipher is selected. Full details of the vulnerability
   are available at: http://www.openssh.com/txt/gcmrekey.adv

Changes since OpenSSH 6.2 is too many to write here, please refer
the release note: http://www.openssh.com/txt/release-6.3.