Change ints to bools around thread_info executing/resumed

Switch thread_info::resumed to bool (thread_info::executing already is a bool),
and try to change everything more or less related to that to consistently use
true/false instead of 1/0.

gdb/ChangeLog:

	* fork-child.c (gdb_startup_inferior): Use bool instead of int.
	* gdbthread.h (class thread_info) <resumed>: Likewise.
	* infrun.c (resume_1): Likewise.
	(proceed): Likewise.
	(infrun_thread_stop_requested): Likewise.
	(stop_all_threads): Likewise.
	(handle_inferior_event): Likewise.
	(restart_threads): Likewise.
	(finish_step_over): Likewise.
	(keep_going_stepped_thread): Likewise.
	* linux-nat.c (attach_proc_task_lwp_callback): Likewise.
	(linux_handle_extended_wait): Likewise.
	* record-btrace.c (get_thread_current_frame_id): Likewise.
	* record-full.c (record_full_wait_1): Likewise.
	* remote.c (remote_target::process_initial_stop_replies): Likewise.
	* target.c (target_resume): Likewise.
	* thread.c (set_running_thread): Likewise.