Reland "Non-SFI mode: Add Linux asynchronous signal support"

src/nonsfi/linux/linux_pthread_private.h

 /*
  * Copyright 2015 The Native Client Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef NATIVE_CLIENT_SRC_NONSFI_LINUX_LINUX_PTHREAD_PRIVATE_H_
 #define NATIVE_CLIENT_SRC_NONSFI_LINUX_LINUX_PTHREAD_PRIVATE_H_ 1
 
 #include <stdint.h>
 
 #include "native_client/src/include/nacl_base.h"
+#include "native_client/src/untrusted/irt/irt.h"
 
 EXTERN_C_BEGIN
 
 /*
  * Creates a new thread by calling clone(). This function does use the |stack|
  * parameter and the thread's entrypoint is |start_func| with |thread_ptr| as
  * its parameter.
  */
 int nacl_user_thread_create(void *(*start_func)(void *), void *stack,
-                            void *thread_ptr);
+                            void *thread_ptr, nacl_irt_tid_t *child_tid);
 
 /*
  * Exits a thread started by |nacl_user_thread_create|. Threads started with
  * pthread_create() should terminate by calling pthread_exit() instead.
  */
 void nacl_user_thread_exit(int32_t *stack_flag);
 
 EXTERN_C_END
 
 #endif