Fix implicit-function-declaration warning.

An include file seems to be missing for

  chacha20poly1305aead.c:72:3: warning: implicit declaration of function
  ‘timingsafe_bcmp’ [-Wimplicit-function-declaration]

Signed-off-by: James Cloos <cloos@jhcloos.com>
Add the chacha20-poly1305 cipher to the ssh_config.5 man page.

Signed-off-by: James Cloos <cloos@jhcloos.com>