crypto/tls: Update references to draft-ietf-tls-downgrade-scsv-00.

It's RFC 7507 now.

Change-Id: Iccd6c65f9d4b1f4d17ee068dee4576a512ba8405
Reviewed-on: https://go-review.googlesource.com/21154
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/src/crypto/tls/cipher_suites.go b/src/crypto/tls/cipher_suites.go
index d4d75cb..e69f5f9 100644
--- a/src/crypto/tls/cipher_suites.go
+++ b/src/crypto/tls/cipher_suites.go
@@ -286,6 +286,6 @@
 
 	// TLS_FALLBACK_SCSV isn't a standard cipher suite but an indicator
 	// that the client is doing version fallback. See
-	// https://tools.ietf.org/html/draft-ietf-tls-downgrade-scsv-00.
+	// https://tools.ietf.org/html/rfc7507.
 	TLS_FALLBACK_SCSV uint16 = 0x5600
 )
diff --git a/src/crypto/tls/handshake_server.go b/src/crypto/tls/handshake_server.go
index d910730..a6cafd3 100644
--- a/src/crypto/tls/handshake_server.go
+++ b/src/crypto/tls/handshake_server.go
@@ -246,7 +246,7 @@
 		return false, errors.New("tls: no cipher suite supported by both client and server")
 	}
 
-	// See https://tools.ietf.org/html/draft-ietf-tls-downgrade-scsv-00.
+	// See https://tools.ietf.org/html/rfc7507.
 	for _, id := range hs.clientHello.cipherSuites {
 		if id == TLS_FALLBACK_SCSV {
 			// The client is doing a fallback connection.