go.crypto/ssh: import gosshnew.

See https://groups.google.com/d/msg/Golang-nuts/AoVxQ4bB5XQ/i8kpMxdbVlEJ

R=hanwen
CC=golang-codereviews
https://golang.org/cl/86190043

ssh/test/forward_unix_test.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin freebsd linux netbsd openbsd plan9
+// +build darwin freebsd linux netbsd openbsd
 
 package test