Add go-charset and chardet to vendor

vendor/github.com/paulrosania/go-charset/charset/ascii.go

@@ -0,0 +1,65 @@
+package charset
+
+import (
+	"bytes"
+	"fmt"
+	"unicode/utf8"
+)
+
+func init() {
+	registerClass("ascii", fromASCII, toASCII)
+}
+
+const errorByte = '?'
+
+type translateFromASCII bool
+
+type codePointError struct {
+	i       int
+	cp      rune
+	charset string
+}
+
+func (e *codePointError) Error() string {
+	return fmt.Sprintf("Parse error at index %n: Code point %n is undefined in %s", e.i, e.cp, e.charset)
+}
+
+func (strict translateFromASCII) Translate(data []byte, eof bool) (int, []byte, error) {
+	buf := bytes.NewBuffer(make([]byte, 0, len(data)))
+	for i, c := range data {
+		if c > 0 && c < 128 {
+			buf.WriteByte(c)
+			if c < 32 && c != 10 && c != 13 && c != 9 {
+				// badly formed
+			}
+		} else {
+			if strict {
+				return 0, nil, &codePointError{i, rune(c), "US-ASCII"}
+			}
+			buf.WriteRune(utf8.RuneError)
+		}
+	}
+	return len(data), buf.Bytes(), nil
+}
+
+type translateToASCII bool
+
+func (strict translateToASCII) Translate(data []byte, eof bool) (int, []byte, error) {
+	buf := bytes.NewBuffer(make([]byte, 0, len(data)))
+	for _, c := range data {
+		if c > 0 && c < 128 {
+			buf.WriteByte(c)
+		} else {
+			buf.WriteByte(errorByte)
+		}
+	}
+	return len(data), buf.Bytes(), nil
+}
+
+func fromASCII(arg string) (Translator, error) {
+	return new(translateFromASCII), nil
+}
+
+func toASCII(arg string) (Translator, error) {
+	return new(translateToASCII), nil
+}