csv, gob, json, mail, mime, xml: use rune

Nothing terribly interesting here.

R=golang-dev, r, borman
CC=golang-dev
https://golang.org/cl/5315043

src/pkg/json/decode_test.go

@@ -243,7 +243,7 @@ func TestHTMLEscape(t *testing.T) {
 	}
 }
 
-func noSpace(c int) int {
+func noSpace(c rune) rune {
 	if isSpace(c) {
 		return -1
 	}