removing fmt dependency from encoding/json

json.patch

diff --git a/src/encoding/json/decode.go b/src/encoding/json/decode.go
index 434edf8..072b570 100644
--- a/src/encoding/json/decode.go
+++ b/src/encoding/json/decode.go
@@ -12,7 +12,6 @@ import (
 	"encoding"
 	"encoding/base64"
 	"errors"
-	"fmt"
 	"reflect"
 	"runtime"
 	"strconv"
@@ -683,7 +682,7 @@ func (d *decodeState) object(v reflect.Value) {
 			case string:
 				d.literalStore([]byte(qv), subv, true)
 			default:
-				d.saveError(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal unquoted value into %v", subv.Type()))
+				d.saveError(errors.New("json: invalid use of ,string struct tag, trying to unmarshal unquoted value into " + subv.Type().String()))
 			}
 		} else {
 			d.value(subv)
@@ -757,7 +756,7 @@ func (d *decodeState) literalStore(item []byte, v reflect.Value, fromQuoted bool
 	// Check for unmarshaler.
 	if len(item) == 0 {
 		//Empty string given
-		d.saveError(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
+		d.saveError(errors.New("json: invalid use of ,string struct tag, trying to unmarshal " + strconv.Quote(string(item)) + " into " + v.Type().String()))
 		return
 	}
 	wantptr := item[0] == 'n' // null
@@ -772,7 +771,7 @@ func (d *decodeState) literalStore(item []byte, v reflect.Value, fromQuoted bool
 	if ut != nil {
 		if item[0] != '"' {
 			if fromQuoted {
-				d.saveError(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
+				d.saveError(errors.New("json: invalid use of ,string struct tag, trying to unmarshal " + strconv.Quote(string(item)) + " into " + v.Type().String()))
 			} else {
 				d.saveError(&UnmarshalTypeError{"string", v.Type(), int64(d.off)})
 			}
@@ -781,7 +780,7 @@ func (d *decodeState) literalStore(item []byte, v reflect.Value, fromQuoted bool
 		s, ok := unquoteBytes(item)
 		if !ok {
 			if fromQuoted {
-				d.error(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
+				d.error(errors.New("json: invalid use of ,string struct tag, trying to unmarshal " + strconv.Quote(string(item)) + " into " + v.Type().String()))
 			} else {
 				d.error(errPhase)
 			}
@@ -807,7 +806,7 @@ func (d *decodeState) literalStore(item []byte, v reflect.Value, fromQuoted bool
 		switch v.Kind() {
 		default:
 			if fromQuoted {
-				d.saveError(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
+				d.saveError(errors.New("json: invalid use of ,string struct tag, trying to unmarshal " + strconv.Quote(string(item)) + " into " + v.Type().String()))
 			} else {
 				d.saveError(&UnmarshalTypeError{"bool", v.Type(), int64(d.off)})
 			}
@@ -825,7 +824,7 @@ func (d *decodeState) literalStore(item []byte, v reflect.Value, fromQuoted bool
 		s, ok := unquoteBytes(item)
 		if !ok {
 			if fromQuoted {
-				d.error(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
+				d.error(errors.New("json: invalid use of ,string struct tag, trying to unmarshal " + strconv.Quote(string(item)) + " into " + v.Type().String()))
 			} else {
 				d.error(errPhase)
 			}
@@ -858,7 +857,7 @@ func (d *decodeState) literalStore(item []byte, v reflect.Value, fromQuoted bool
 	default: // number
 		if c != '-' && (c < '0' || c > '9') {
 			if fromQuoted {
-				d.error(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
+				d.error(errors.New("json: invalid use of ,string struct tag, trying to unmarshal " + strconv.Quote(string(item)) + " into " + v.Type().String()))
 			} else {
 				d.error(errPhase)
 			}
@@ -869,12 +868,12 @@ func (d *decodeState) literalStore(item []byte, v reflect.Value, fromQuoted bool
 			if v.Kind() == reflect.String && v.Type() == numberType {
 				v.SetString(s)
 				if !isValidNumber(s) {
-					d.error(fmt.Errorf("json: invalid number literal, trying to unmarshal %q into Number", item))
+					d.error(errors.New("json: invalid number literal, trying to unmarshal " + strconv.Quote(string(item)) + " into Number"))
 				}
 				break
 			}
 			if fromQuoted {
-				d.error(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
+				d.error(errors.New("json: invalid use of ,string struct tag, trying to unmarshal " + strconv.Quote(string(item)) + " into " + v.Type().String()))
 			} else {
 				d.error(&UnmarshalTypeError{"number", v.Type(), int64(d.off)})
 			}
diff --git a/src/encoding/json/encode.go b/src/encoding/json/encode.go
index d8c7798..24c1582 100644
--- a/src/encoding/json/encode.go
+++ b/src/encoding/json/encode.go
@@ -14,7 +14,7 @@ import (
 	"bytes"
 	"encoding"
 	"encoding/base64"
-	"fmt"
+	"errors"
 	"math"
 	"reflect"
 	"runtime"
@@ -544,7 +544,7 @@ func stringEncoder(e *encodeState, v reflect.Value, opts encOpts) {
 			numStr = "0" // Number's zero-val
 		}
 		if !isValidNumber(numStr) {
-			e.error(fmt.Errorf("json: invalid number literal %q", numStr))
+			e.error(errors.New("json: invalid number literal " + strconv.Quote(numStr)))
 		}
 		e.WriteString(numStr)
 		return