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.go

@@ -363,7 +363,6 @@ func Repeat(s string, count int) string {
 	return string(b)
 }
 
-
 // ToUpper returns a copy of the string s with all Unicode letters mapped to their upper case.
 func ToUpper(s string) string { return Map(unicode.ToUpper, s) }