Update vendor/

vendor/github.com/emersion/go-imap/utf7/utf7.go

@@ -3,6 +3,8 @@ package utf7
 
 import (
 	"encoding/base64"
+
+	"golang.org/x/text/encoding"
 )
 
 const (
@@ -12,4 +14,21 @@ const (
 	repl = '\uFFFD' // Unicode replacement code point
 )
 
-var enc = base64.NewEncoding("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,")
+var b64Enc = base64.NewEncoding("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,")
+
+type enc struct{}
+
+func (e enc) NewDecoder() *encoding.Decoder {
+	return &encoding.Decoder{
+		Transformer: &decoder{true},
+	}
+}
+
+func (e enc) NewEncoder() *encoding.Encoder {
+	return &encoding.Encoder{
+		Transformer: &encoder{},
+	}
+}
+
+// Encoding is the modified UTF-7 encoding.
+var Encoding encoding.Encoding = enc{}