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/xml/xml_test.go

@@ -546,7 +546,6 @@ func TestEntityInsideCDATA(t *testing.T) {
 	}
 }
 
-
 // The last three tests (respectively one for characters in attribute
 // names and two for character entities) pass not because of code
 // changed for issue 1259, but instead pass with the given messages
@@ -567,7 +566,6 @@ var characterTests = []struct {
 	{"<doc>&\xef\xbf\xbe;</doc>", "invalid character entity &;"},
 }
 
-
 func TestDisallowedCharacters(t *testing.T) {
 
 	for i, tt := range characterTests {