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-gss.h b/ssh-gss.h
index c29a1b7..a99d7f0 100644
--- a/ssh-gss.h
+++ b/ssh-gss.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-gss.h,v 1.10 2007/06/12 08:20:00 djm Exp $ */
+/* $OpenBSD: ssh-gss.h,v 1.11 2014/02/26 20:28:44 djm Exp $ */
 /*
  * Copyright (c) 2001-2003 Simon Wilkinson. All rights reserved.
  *
@@ -42,12 +42,13 @@
 #   include <gssapi/gssapi_generic.h>
 #  endif
 
-/* MIT Kerberos doesn't seem to define GSS_NT_HOSTBASED_SERVICE */
+/* Old MIT Kerberos doesn't seem to define GSS_NT_HOSTBASED_SERVICE */
 
-#ifndef GSS_C_NT_HOSTBASED_SERVICE
-#define GSS_C_NT_HOSTBASED_SERVICE gss_nt_service_name
-#endif /* GSS_C_NT_... */
-#endif /* !HEIMDAL */
+#  if !HAVE_DECL_GSS_C_NT_HOSTBASED_SERVICE
+#   define GSS_C_NT_HOSTBASED_SERVICE gss_nt_service_name
+#  endif /* !HAVE_DECL_GSS_C_NT_... */
+
+# endif /* !HEIMDAL */
 #endif /* KRB5 */
 
 /* draft-ietf-secsh-gsskeyex-06 */
@@ -103,6 +104,8 @@
 void ssh_gssapi_set_oid(Gssctxt *, gss_OID);
 void ssh_gssapi_supported_oids(gss_OID_set *);
 ssh_gssapi_mech *ssh_gssapi_get_ctype(Gssctxt *);
+void ssh_gssapi_prepare_supported_oids(void);
+OM_uint32 ssh_gssapi_test_oid_supported(OM_uint32 *, gss_OID, int *);
 
 OM_uint32 ssh_gssapi_import_name(Gssctxt *, const char *);
 OM_uint32 ssh_gssapi_init_ctx(Gssctxt *, int,