external/openssh: update to 6.8p1.

In preparation for some updates to external/openssh to make it work with
BoringSSL, this change updates the code to a recent version. The current
version (5.9p1) is coming up on four years old now.

  * Confirmed that f5c67b478bef9992de9e9ec91ce10af4f6205e0d matches
    OpenSSH 5.9p1 exactly (save for the removal of the scard
    subdirectory).

  * Downloaded openssh-6.8p1.tar.gz (SHA256:
    3ff64ce73ee124480b5bf767b9830d7d3c03bbcb6abe716b78f0192c37ce160e)
    and verified with PGP signature. (I've verified Damien's key in
    person previously.)

  * Applied changes between f5c67b478bef9992de9e9ec91ce10af4f6205e0d and
    OpenSSH 5.9p1 to 6.8p1 and updated the build as best I can. The
    ugliest change is probably the duplication of umac.c to umac128.c
    because Android conditionally compiles that file twice. See the
    comment in those files.

Change-Id: I63cb07a8118afb5a377f116087a0882914cea486
diff --git a/auth-options.h b/auth-options.h
index 7455c94..34852e5 100644
--- a/auth-options.h
+++ b/auth-options.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: auth-options.h,v 1.20 2010/05/07 11:30:29 djm Exp $ */
+/* $OpenBSD: auth-options.h,v 1.21 2015/01/14 10:30:34 markus Exp $ */
 
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
@@ -35,6 +35,6 @@
 
 int	auth_parse_options(struct passwd *, char *, char *, u_long);
 void	auth_clear_options(void);
-int	auth_cert_options(Key *, struct passwd *);
+int	auth_cert_options(struct sshkey *, struct passwd *);
 
 #endif