crypto/tls: document that the package supports TLS 1.2

Fixes #6456.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/13740047

common.go

@@ -248,7 +248,7 @@ type Config struct {
 
 	// MaxVersion contains the maximum SSL/TLS version that is acceptable.
 	// If zero, then the maximum version supported by this package is used,
-	// which is currently TLS 1.1.
+	// which is currently TLS 1.2.
 	MaxVersion uint16
 
 	serverInitOnce sync.Once // guards calling (*Config).serverInit

tls.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.
 
-// Package tls partially implements TLS 1.1, as specified in RFC 4346.
+// Package tls partially implements TLS 1.2, as specified in RFC 4346.
 package tls
 
 import (