Update Obfs4proxy to release 0.0.13.

build.sh

@@ -34,7 +34,7 @@ else
     # No .git directory - That's a normal install.
     git clone https://gitlab.com/yawning/obfs4.git
     cd obfs4 || exit 1
-    git checkout --force --quiet cbf3f3cf
+    git checkout --force --quiet 77af0cba
     cd ..
     git clone https://git.torproject.org/pluggable-transports/snowflake.git
     cd snowflake || exit 1

obfs4 @ 77af0cba

-Subproject commit cbf3f3cfa09cf48c42aebd1b96fd7952f1ddb25d
+Subproject commit 77af0cba934d73c4baeb709560bcfc9a9fbc661c

obfs4.patch

 diff --git a/obfs4proxy/obfs4proxy.go b/obfs4proxy/obfs4proxy.go
-index 628f56b..be2cc55 100644
+index d92f5f5..df2584e 100644
 --- a/obfs4proxy/obfs4proxy.go
 +++ b/obfs4proxy/obfs4proxy.go
 @@ -27,10 +27,9 @@