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/auth2-passwd.c b/auth2-passwd.c
index 4dd3816..09cf077 100644
--- a/auth2-passwd.c
+++ b/auth2-passwd.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: auth2-passwd.c,v 1.9 2006/08/03 03:34:41 deraadt Exp $ */
+/* $OpenBSD: auth2-passwd.c,v 1.12 2014/07/15 15:54:14 millert Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  *
@@ -41,6 +41,7 @@
 #include "ssh-gss.h"
 #endif
 #include "monitor_wrap.h"
+#include "misc.h"
 #include "servconf.h"
 
 /* import */
@@ -59,20 +60,20 @@
 	if (change) {
 		/* discard new password from packet */
 		newpass = packet_get_string(&newlen);
-		memset(newpass, 0, newlen);
-		xfree(newpass);
+		explicit_bzero(newpass, newlen);
+		free(newpass);
 	}
 	packet_check_eom();
 
 	if (change)
 		logit("password change not supported");
-#ifndef ANDROID
-	/* no password authentication in android */
+#if !defined(ANDROID)
+	/* no password authentication in Android */
 	else if (PRIVSEP(auth_password(authctxt, password)) == 1)
 		authenticated = 1;
 #endif
-	memset(password, 0, len);
-	xfree(password);
+	explicit_bzero(password, len);
+	free(password);
 	return authenticated;
 }