strconv: fix typo in docs

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/12709044

src/pkg/strconv/quote.go

@@ -133,7 +133,7 @@ func QuoteRuneToASCII(r rune) string {
 	return quoteWith(string(r), '\'', true)
 }
 
-// AppendQuoteRune appends a single-quoted Go character literal representing the rune,
+// AppendQuoteRuneToASCII appends a single-quoted Go character literal representing the rune,
 // as generated by QuoteRuneToASCII, to dst and returns the extended buffer.
 func AppendQuoteRuneToASCII(dst []byte, r rune) []byte {
 	return append(dst, QuoteRuneToASCII(r)...)