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/ssh-pkcs11.h b/ssh-pkcs11.h
index 59f456a..0ced74f 100644
--- a/ssh-pkcs11.h
+++ b/ssh-pkcs11.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-pkcs11.h,v 1.2 2010/02/24 06:12:53 djm Exp $ */
+/* $OpenBSD: ssh-pkcs11.h,v 1.4 2015/01/15 09:40:00 djm Exp $ */
 /*
  * Copyright (c) 2010 Markus Friedl.  All rights reserved.
  *
@@ -16,5 +16,9 @@
  */
 int	pkcs11_init(int);
 void	pkcs11_terminate(void);
-int	pkcs11_add_provider(char *, char *, Key ***);
+int	pkcs11_add_provider(char *, char *, struct sshkey ***);
 int	pkcs11_del_provider(char *);
+
+#if !defined(WITH_OPENSSL) && defined(ENABLE_PKCS11)
+#undef ENABLE_PKCS11
+#endif