strconv: remove unused append rune width param

Found by github.com/mvdan/unparam. Small performance win when the
utf8.RuneLen call is removed.

name               old time/op    new time/op    delta
AppendQuoteRune-4    21.7ns ± 0%    21.4ns ± 0%  -1.38%  (p=0.008 n=5+5)

Change-Id: Ieb3b3e1148db7a3d854c81555a491edeff549f43
Reviewed-on: https://go-review.googlesource.com/37831Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/strconv/quote.go

@@ -32,7 +32,7 @@ func appendQuotedWith(buf []byte, s string, quote byte, ASCIIonly, graphicOnly b
 			buf = append(buf, lowerhex[s[0]&0xF])
 			continue
 		}
-		buf = appendEscapedRune(buf, r, width, quote, ASCIIonly, graphicOnly)
+		buf = appendEscapedRune(buf, r, quote, ASCIIonly, graphicOnly)
 	}
 	buf = append(buf, quote)
 	return buf
@@ -43,12 +43,12 @@ func appendQuotedRuneWith(buf []byte, r rune, quote byte, ASCIIonly, graphicOnly
 	if !utf8.ValidRune(r) {
 		r = utf8.RuneError
 	}
-	buf = appendEscapedRune(buf, r, utf8.RuneLen(r), quote, ASCIIonly, graphicOnly)
+	buf = appendEscapedRune(buf, r, quote, ASCIIonly, graphicOnly)
 	buf = append(buf, quote)
 	return buf
 }
 
-func appendEscapedRune(buf []byte, r rune, width int, quote byte, ASCIIonly, graphicOnly bool) []byte {
+func appendEscapedRune(buf []byte, r rune, quote byte, ASCIIonly, graphicOnly bool) []byte {
 	var runeTmp [utf8.UTFMax]byte
 	if r == rune(quote) || r == '\\' { // always backslashed
 		buf = append(buf, '\\')