Rename NewEncoder-->newEncoder

pkgs/erasure/decode.go

@@ -112,6 +112,6 @@ func (e *Encoder) Decode(chunks [][]byte, length int) ([]byte, error) {
 }
 
 func Decode(block [][]byte, ep *EncoderParams, length int) ([]byte, error) {
-	encoder := NewEncoder(ep)
+	encoder := newEncoder(ep)
 	return encoder.Decode(block, length)
 }

pkgs/erasure/encode.go

@@ -152,6 +152,6 @@ func (e *Encoder) Encode(block []byte) ([][]byte, int) {
 }
 
 func Encode(block []byte, ep *EncoderParams) ([][]byte, int) {
-	encoder := NewEncoder(ep)
+	encoder := newEncoder(ep)
 	return encoder.Encode(block)
 }