vendor: update all dependencies to latest versions

vendor/golang.org/x/sys/plan9/asm.s

@@ -1,4 +1,4 @@
-// Copyright 2014 The Go Authors.  All rights reserved.
+// Copyright 2014 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 

vendor/golang.org/x/sys/plan9/env_plan9.go

@@ -1,4 +1,4 @@
-// Copyright 2011 The Go Authors.  All rights reserved.
+// Copyright 2011 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
@@ -25,3 +25,7 @@ func Clearenv() {
 func Environ() []string {
 	return syscall.Environ()
 }
+
+func Unsetenv(key string) error {
+	return syscall.Unsetenv(key)
+}

vendor/golang.org/x/sys/plan9/env_unset.go

@@ -1,14 +0,0 @@
-// Copyright 2014 The Go Authors.  All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// +build go1.4
-
-package plan9
-
-import "syscall"
-
-func Unsetenv(key string) error {
-	// This was added in Go 1.4.
-	return syscall.Unsetenv(key)
-}

vendor/golang.org/x/sys/plan9/errors_plan9.go

@@ -1,4 +1,4 @@
-// Copyright 2011 The Go Authors.  All rights reserved.
+// Copyright 2011 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 

vendor/golang.org/x/sys/plan9/race.go

@@ -1,4 +1,4 @@
-// Copyright 2012 The Go Authors.  All rights reserved.
+// Copyright 2012 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 

vendor/golang.org/x/sys/plan9/race0.go

@@ -1,4 +1,4 @@
-// Copyright 2012 The Go Authors.  All rights reserved.
+// Copyright 2012 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 

vendor/golang.org/x/sys/plan9/syscall.go

@@ -5,10 +5,10 @@
 // +build plan9
 
 // Package plan9 contains an interface to the low-level operating system
-// primitives.  OS details vary depending on the underlying system, and
+// primitives. OS details vary depending on the underlying system, and
 // by default, godoc will display the OS-specific documentation for the current
-// system.  If you want godoc to display documentation for another
-// system, set $GOOS and $GOARCH to the desired system.  For example, if
+// system. If you want godoc to display documentation for another
+// system, set $GOOS and $GOARCH to the desired system. For example, if
 // you want to view documentation for freebsd/arm on linux/amd64, set $GOOS
 // to freebsd and $GOARCH to arm.
 // The primary use of this package is inside other packages that provide a more