SSHd: add ETM MACs for SHA2

Should be in since 6.1 (but tested with OpenSSH 6.4).
Added myself to the reviewers list
Should really learn the alphabet...
Tested with OpenSSH 6.4, too
Optional: Whitelist static users for login

Quite conservative but useful for systems with a very limited number
of allowed system users for SSH.
spaces -> tabs
Add intermediate aes192-ctr

Won't harm and increases available ciphers
Remove AllowUsers

Too specific. Thanks to @azet for the feedback!
Remove aes-192 for now
ETM for SSH2 was introduced in OpenSSH 6.2

I tested the settings for OpenSSH 6.4.
Release log for OpenSSH 6.2: http://www.openssh.com/txt/release-6.2
Only advertise OpenSSH 6.4

GCM, UMAC and ETM added in 6.2, but due to a memory corruption vulnerability
in 6.2 and 6.3 by an insecure GCM implementation
  http://www.openssh.com/txt/gcmrekey.adv
we only recommend OpenSSH 6.4+
  http://www.openssh.com/txt/release-6.4
Merge pull request #32 from ax3l/ssh-moreEtmMacs

SSHd: add ETM MACs for SHA2