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/fe25519.h b/fe25519.h
new file mode 100644
index 0000000..41b3cbb
--- /dev/null
+++ b/fe25519.h
@@ -0,0 +1,70 @@
+/* $OpenBSD: fe25519.h,v 1.3 2013/12/09 11:03:45 markus Exp $ */
+
+/*
+ * Public Domain, Authors: Daniel J. Bernstein, Niels Duif, Tanja Lange,
+ * Peter Schwabe, Bo-Yin Yang.
+ * Copied from supercop-20130419/crypto_sign/ed25519/ref/fe25519.h
+ */
+
+#ifndef FE25519_H
+#define FE25519_H
+
+#include "crypto_api.h"
+
+#define fe25519              crypto_sign_ed25519_ref_fe25519
+#define fe25519_freeze       crypto_sign_ed25519_ref_fe25519_freeze
+#define fe25519_unpack       crypto_sign_ed25519_ref_fe25519_unpack
+#define fe25519_pack         crypto_sign_ed25519_ref_fe25519_pack
+#define fe25519_iszero       crypto_sign_ed25519_ref_fe25519_iszero
+#define fe25519_iseq_vartime crypto_sign_ed25519_ref_fe25519_iseq_vartime
+#define fe25519_cmov         crypto_sign_ed25519_ref_fe25519_cmov
+#define fe25519_setone       crypto_sign_ed25519_ref_fe25519_setone
+#define fe25519_setzero      crypto_sign_ed25519_ref_fe25519_setzero
+#define fe25519_neg          crypto_sign_ed25519_ref_fe25519_neg
+#define fe25519_getparity    crypto_sign_ed25519_ref_fe25519_getparity
+#define fe25519_add          crypto_sign_ed25519_ref_fe25519_add
+#define fe25519_sub          crypto_sign_ed25519_ref_fe25519_sub
+#define fe25519_mul          crypto_sign_ed25519_ref_fe25519_mul
+#define fe25519_square       crypto_sign_ed25519_ref_fe25519_square
+#define fe25519_invert       crypto_sign_ed25519_ref_fe25519_invert
+#define fe25519_pow2523      crypto_sign_ed25519_ref_fe25519_pow2523
+
+typedef struct 
+{
+  crypto_uint32 v[32]; 
+}
+fe25519;
+
+void fe25519_freeze(fe25519 *r);
+
+void fe25519_unpack(fe25519 *r, const unsigned char x[32]);
+
+void fe25519_pack(unsigned char r[32], const fe25519 *x);
+
+int fe25519_iszero(const fe25519 *x);
+
+int fe25519_iseq_vartime(const fe25519 *x, const fe25519 *y);
+
+void fe25519_cmov(fe25519 *r, const fe25519 *x, unsigned char b);
+
+void fe25519_setone(fe25519 *r);
+
+void fe25519_setzero(fe25519 *r);
+
+void fe25519_neg(fe25519 *r, const fe25519 *x);
+
+unsigned char fe25519_getparity(const fe25519 *x);
+
+void fe25519_add(fe25519 *r, const fe25519 *x, const fe25519 *y);
+
+void fe25519_sub(fe25519 *r, const fe25519 *x, const fe25519 *y);
+
+void fe25519_mul(fe25519 *r, const fe25519 *x, const fe25519 *y);
+
+void fe25519_square(fe25519 *r, const fe25519 *x);
+
+void fe25519_invert(fe25519 *r, const fe25519 *x);
+
+void fe25519_pow2523(fe25519 *r, const fe25519 *x);
+
+#endif