encoding/hex: fix typo

Thanks to avadh4all for spotting it.

Fixes #1214.

R=r, r2
CC=golang-dev
https://golang.org/cl/2616041

src/pkg/encoding/hex/hex.go

@@ -71,7 +71,7 @@ func Decode(dst, src []byte) (int, os.Error) {
 // fromHexChar converts a hex character into its value and a success flag.
 func fromHexChar(c byte) (byte, bool) {
 	switch {
-	case 0 <= c && c <= '9':
+	case '0' <= c && c <= '9':
 		return c - '0', true
 	case 'a' <= c && c <= 'f':
 		return c - 'a' + 10, true

src/pkg/encoding/hex/hex_test.go

@@ -58,6 +58,7 @@ var decodeTests = []decodeTest{
 	decodeTest{[]byte{}, []byte{}, true},
 	decodeTest{[]byte{'0'}, []byte{}, false},
 	decodeTest{[]byte{'0', 'g'}, []byte{}, false},
+	decodeTest{[]byte{'0', '\x01'}, []byte{}, false},
 	decodeTest{[]byte{'0', '0'}, []byte{0}, true},
 	decodeTest{[]byte{'0', '1'}, []byte{1}, true},
 	decodeTest{[]byte{'0', '2'}, []byte{2}, true},
@@ -129,6 +130,7 @@ var decodeStringTests = []decodeStringTest{
 	decodeStringTest{"", []byte{}, true},
 	decodeStringTest{"0", []byte{}, false},
 	decodeStringTest{"00", []byte{0}, true},
+	decodeStringTest{"0\x01", []byte{}, false},
 	decodeStringTest{"0g", []byte{}, false},
 	decodeStringTest{"00ff00", []byte{0, 255, 0}, true},
 	decodeStringTest{"0000ff", []byte{0, 0, 255}, true},