strconv: add example for QuoteRuneToGraphic and QuoteToGraphic functions

Change-Id: Ie5b2ef0087dbc7b8191de8c8b4190396631e3c7f
Reviewed-on: https://go-review.googlesource.com/c/137215
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/strconv/example_test.go

@@ -265,7 +265,7 @@ func ExampleParseUint() {
 }
 
 func ExampleQuote() {
-	s := strconv.Quote(`"Fran & Freddie's Diner	☺"`)
+	s := strconv.Quote(`"Fran & Freddie's Diner	☺"`) // there is a tab character inside the string literal
 	fmt.Println(s)
 
 	// Output:
@@ -288,14 +288,50 @@ func ExampleQuoteRuneToASCII() {
 	// '\u263a'
 }
 
+func ExampleQuoteRuneToGraphic() {
+	s := strconv.QuoteRuneToGraphic('☺')
+	fmt.Println(s)
+
+	s = strconv.QuoteRuneToGraphic('\u263a')
+	fmt.Println(s)
+
+	s = strconv.QuoteRuneToGraphic('\u000a')
+	fmt.Println(s)
+
+	s = strconv.QuoteRuneToGraphic('	') // tab character
+	fmt.Println(s)
+
+	// Output:
+	// '☺'
+	// '☺'
+	// '\n'
+	// '\t'
+}
+
 func ExampleQuoteToASCII() {
-	s := strconv.QuoteToASCII(`"Fran & Freddie's Diner	☺"`)
+	s := strconv.QuoteToASCII(`"Fran & Freddie's Diner	☺"`) // there is a tab character inside the string literal
 	fmt.Println(s)
 
 	// Output:
 	// "\"Fran & Freddie's Diner\t\u263a\""
 }
 
+func ExampleQuoteToGraphic() {
+	s := strconv.QuoteToGraphic("☺")
+	fmt.Println(s)
+
+	s = strconv.QuoteToGraphic("This is a \u263a	\u000a") // there is a tab character inside the string literal
+	fmt.Println(s)
+
+	s = strconv.QuoteToGraphic(`" This is a ☺ \n "`)
+	fmt.Println(s)
+
+	// Output:
+	// "☺"
+	// "This is a ☺\t\n"
+	// "\" This is a ☺ \\n \""
+}
+
 func ExampleUnquote() {
 	s, err := strconv.Unquote("You can't unquote a string without quotes")
 	fmt.Printf("%q, %v\n", s, err)