PHP 预定义常量 Newt form exit reasons

Newt form exit reasons

**Newt form exit reasons**
constant	meaning
`NEWT_EXIT_HOTKEY`	hotkey defined by newt_form_add_hot_key() was pressed
`NEWT_EXIT_COMPONENT`	some component has caused form to exit
`NEWT_EXIT_FDREADY`	file descriptor specified in newt_form_watch_fd() is ready to be read or written to
`NEWT_EXIT_TIMER`	time specified in newt_form_set_timer() has elapsed