[project] change syscall to /x/sys/unix|windows

Changes most references of syscall to golang.org/x/sys/
Ones aren't changes include, Errno, Signal and SysProcAttr
as they haven't been implemented in /x/sys/.

Signed-off-by: Christopher Jones <tophj@linux.vnet.ibm.com>

[s390x] switch utsname from unsigned to signed

per 33267e036f
char in s390x in the /x/sys/unix package is now signed, so
change the buildtags

Signed-off-by: Christopher Jones <tophj@linux.vnet.ibm.com>

pkg/pidfile/pidfile_darwin.go

@@ -3,12 +3,12 @@
 package pidfile
 
 import (
-	"syscall"
+	"golang.org/x/sys/unix"
 )
 
 func processExists(pid int) bool {
 	// OS X does not have a proc filesystem.
 	// Use kill -0 pid to judge if the process exists.
-	err := syscall.Kill(pid, 0)
+	err := unix.Kill(pid, 0)
 	return err == nil
 }

pkg/pidfile/pidfile_windows.go

@@ -1,6 +1,8 @@
 package pidfile
 
-import "syscall"
+import (
+	"golang.org/x/sys/windows"
+)
 
 const (
 	processQueryLimitedInformation = 0x1000
@@ -9,13 +11,13 @@ const (
 )
 
 func processExists(pid int) bool {
-	h, err := syscall.OpenProcess(processQueryLimitedInformation, false, uint32(pid))
+	h, err := windows.OpenProcess(processQueryLimitedInformation, false, uint32(pid))
 	if err != nil {
 		return false
 	}
 	var c uint32
-	err = syscall.GetExitCodeProcess(h, &c)
-	syscall.Close(h)
+	err = windows.GetExitCodeProcess(h, &c)
+	windows.Close(h)
 	if err != nil {
 		return c == stillActive
 	}