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/cipher-chachapoly.h b/cipher-chachapoly.h
new file mode 100644
index 0000000..b7072be
--- /dev/null
+++ b/cipher-chachapoly.h
@@ -0,0 +1,41 @@
+/* $OpenBSD: cipher-chachapoly.h,v 1.4 2014/06/24 01:13:21 djm Exp $ */
+
+/*
+ * Copyright (c) Damien Miller 2013 <djm@mindrot.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+#ifndef CHACHA_POLY_AEAD_H
+#define CHACHA_POLY_AEAD_H
+
+#include <sys/types.h>
+#include "chacha.h"
+#include "poly1305.h"
+
+#define CHACHA_KEYLEN	32 /* Only 256 bit keys used here */
+
+struct chachapoly_ctx {
+	struct chacha_ctx main_ctx, header_ctx;
+};
+
+int	chachapoly_init(struct chachapoly_ctx *cpctx,
+    const u_char *key, u_int keylen)
+    __attribute__((__bounded__(__buffer__, 2, 3)));
+int	chachapoly_crypt(struct chachapoly_ctx *cpctx, u_int seqnr,
+    u_char *dest, const u_char *src, u_int len, u_int aadlen, u_int authlen,
+    int do_encrypt);
+int	chachapoly_get_length(struct chachapoly_ctx *cpctx,
+    u_int *plenp, u_int seqnr, const u_char *cp, u_int len)
+    __attribute__((__bounded__(__buffer__, 4, 5)));
+
+#endif /* CHACHA_POLY_AEAD_H */