Replace RE2 import with a dependency

third_party/re2/util/thread.cc

-// Copyright 2009 The RE2 Authors.  All Rights Reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-#include "util/thread.h"
-#include "util/util.h"
-
-Thread::Thread() {
-  pid_ = 0;
-  running_ = 0;
-  joinable_ = 0;
-}
-
-Thread::~Thread() {
-}
-
-void *startThread(void *v) {
-  Thread* t = (Thread*)v;
-  t->Run();
-  return 0;
-}
-
-void Thread::Start() {
-  CHECK(!running_);
-  pthread_create(&pid_, 0, startThread, this);
-  running_ = true;
-  if (!joinable_)
-    pthread_detach(pid_);
-}
-
-void Thread::Join() {
-  CHECK(running_);
-  CHECK(joinable_);
-  void *val;
-  pthread_join(pid_, &val);
-  running_ = 0;
-}
-
-void Thread::SetJoinable(bool j) {
-  CHECK(!running_);
-  joinable_ = j;
-}