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/entropy.h b/entropy.h
index ec1ebcc..c3d78db 100644
--- a/entropy.h
+++ b/entropy.h
@@ -22,7 +22,7 @@
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-/* $Id: entropy.h,v 1.5 2005/09/27 12:46:32 dtucker Exp $ */
+/* $Id: entropy.h,v 1.6 2011/09/09 01:29:41 dtucker Exp $ */
 
 #ifndef _RANDOMS_H
 #define _RANDOMS_H
@@ -30,7 +30,6 @@
 #include "buffer.h"
 
 void seed_rng(void);
-void init_rng(void);
 
 void rexec_send_rng_seed(Buffer *);
 void rexec_recv_rng_seed(Buffer *);