doc/play: don't use println in examples

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/6849105

doc/play/fib.go

 package main
 
+import "fmt"
+
 // fib returns a function that returns
 // successive Fibonacci numbers.
 func fib() func() int {
@@ -13,5 +15,5 @@ func fib() func() int {
 func main() {
 	f := fib()
 	// Function calls are evaluated left-to-right.
-	println(f(), f(), f(), f(), f())
+	fmt.Println(f(), f(), f(), f(), f())
 }

doc/play/sieve.go

@@ -2,6 +2,8 @@
 
 package main
 
+import "fmt"
+
 // Send the sequence 2, 3, 4, ... to channel 'ch'.
 func Generate(ch chan<- int) {
 	for i := 2; ; i++ {
@@ -26,7 +28,7 @@ func main() {
 	go Generate(ch)      // Launch Generate goroutine.
 	for i := 0; i < 10; i++ {
 		prime := <-ch
-		print(prime, "\n")
+		fmt.Println(prime)
 		ch1 := make(chan int)
 		go Filter(ch, ch1, prime)
 		ch = ch1

doc/play/solitaire.go

@@ -89,7 +89,7 @@ func solve() bool {
 					// see if this new board has a solution
 					if solve() {
 						unmove(pos, dir)
-						println(string(board))
+						fmt.Println(string(board))
 						return true
 					}
 					unmove(pos, dir)
@@ -102,7 +102,7 @@ func solve() bool {
 	// tried each possible move
 	if n == 1 && (center < 0 || last == center) {
 		// there's only one peg left
-		println(string(board))
+		fmt.Println(string(board))
 		return true
 	}
 	// no solution found for this board