go/printer: changed max. number of newlines from 3 to 2

manual changes in src/pkg/go/printer, src/cmd/gofix/signal_test.go
(cd src/cmd/gofix/testdata; gofmt -w *.in *.out)
(cd src/pkg/go/printer; gotest -update)
gofmt -w misc src

runs all tests

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/4715041

src/pkg/strings/strings_test.go

@@ -170,7 +170,6 @@ func BenchmarkIndex(b *testing.B) {
 	}
 }
 
-
 type ExplodeTest struct {
 	s string
 	n int
@@ -325,7 +324,6 @@ func TestFieldsFunc(t *testing.T) {
 	}
 }
 
-
 // Test case for any function which accepts and returns a single string.
 type StringTest struct {
 	in, out string