* pinfo.h (class push_process_state): New class to push a process state

	* pinfo.h (class push_process_state): New class to push a process state
	flag temporarily into myself->process_state.
	* fhandler_console.cc (fhandler_console::read): Add push_process_state
	handler.
	(fhandler_console::write): Call bg_check from here.  Add
	push_process_state handler.
	* fhandler_tty.cc (fhandler_tty_slave::write): Ditto.
	(fhandler_tty_slave::read): Ditto.
	(fhandler_pty_master::write): Ditto.
	(fhandler_pty_master::read): Ditto.
	* syscalls.cc (readv): Remove bg_check call and setting process state.
	(writev): Ditto.