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/hmac.h b/hmac.h
new file mode 100644
index 0000000..42b33d0
--- /dev/null
+++ b/hmac.h
@@ -0,0 +1,38 @@
+/* $OpenBSD: hmac.h,v 1.9 2014/06/24 01:13:21 djm Exp $ */
+/*
+ * Copyright (c) 2014 Markus Friedl.  All rights reserved.
+ *
+ * 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 _HMAC_H
+#define _HMAC_H
+
+/* Returns the algorithm's digest length in bytes or 0 for invalid algorithm */
+size_t ssh_hmac_bytes(int alg);
+
+struct sshbuf;
+struct ssh_hmac_ctx;
+struct ssh_hmac_ctx *ssh_hmac_start(int alg);
+
+/* Sets the state of the HMAC or resets the state if key == NULL */
+int ssh_hmac_init(struct ssh_hmac_ctx *ctx, const void *key, size_t klen)
+	__attribute__((__bounded__(__buffer__, 2, 3)));
+int ssh_hmac_update(struct ssh_hmac_ctx *ctx, const void *m, size_t mlen)
+	__attribute__((__bounded__(__buffer__, 2, 3)));
+int ssh_hmac_update_buffer(struct ssh_hmac_ctx *ctx, const struct sshbuf *b);
+int ssh_hmac_final(struct ssh_hmac_ctx *ctx, u_char *d, size_t dlen)
+	__attribute__((__bounded__(__buffer__, 2, 3)));
+void ssh_hmac_free(struct ssh_hmac_ctx *ctx);
+
+#endif /* _HMAC_H */