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/syscall/exec_unix.go

@@ -87,7 +87,6 @@ func SetNonblock(fd int, nonblocking bool) (errno int) {
 	return err
 }
 
-
 // Fork, dup fd onto 0..len(fd), and exec(argv0, argvv, envv) in child.
 // If a dup or exec fails, write the errno int to pipe.
 // (Pipe is close-on-exec so if exec succeeds, it will be closed.)