Use ptid_t.tid to store thread ids instead of ptid_t.pid.

	Use ptid_t.tid to store thread ids instead of ptid_t.pid.

	* remote.c (magic_null_ptid, not_sent_ptid, any_thread_ptid): New
	globals.
	(general_thread, continue_thread): Change type to ptid_t.
	(record_currthread): Take a ptid_t parameter instead of an
	integer.
	(MAGIC_NULL_PID): Delete.
	(set_thread): Take a ptid_t parameter and adjust.
	(set_general_thread, set_continue_thread): New.
	(remote_thread_alive, remote_newthread_step)
	(remote_current_thread, remote_find_new_threads)
	(remote_threads_info, remote_start_remote, remote_vcont_resume)
	(remote_resume_1, remote_wait, extended_remote_create_inferior_1)
	(threadalive_test, remote_pid_to_str)
	(remote_get_thread_local_address): Adjust.
	(_initialize_remote): Initialize magic_null_ptid, not_sent_ptid
	and any_thread_ptid.