migrate to go.sys subrepository

As of go version 1.4 the standard library syscall package is "locked
down" and code outside of the standard library is recommended to migrate
to the go.sys subrepository.

Reference: https://golang.org/s/go1.4-syscall

client/cli/cli.go

@@ -2,12 +2,12 @@ package cli
 
 import (
 	"fmt"
+	sys "golang.org/x/sys/unix"
 	"io"
 	"os"
 	"os/exec"
 	"os/signal"
 	"strings"
-	"syscall"
 
 	"github.com/derekparker/delve/command"
 	"github.com/derekparker/delve/goreadline"
@@ -49,7 +49,7 @@ func Run(run bool, pid int, args []string) {
 	}
 
 	ch := make(chan os.Signal)
-	signal.Notify(ch, syscall.SIGINT)
+	signal.Notify(ch, sys.SIGINT)
 	go func() {
 		for _ = range ch {
 			if dbp.Running() {
@@ -105,7 +105,7 @@ func handleExit(dbp *proctl.DebuggedProcess, status int) {
 	}
 
 	fmt.Println("Detaching from process...")
-	err := syscall.PtraceDetach(dbp.Process.Pid)
+	err := sys.PtraceDetach(dbp.Process.Pid)
 	if err != nil {
 		die(2, "Could not detach", err)
 	}