gdb

gdb
	* python/py-inferior.c (python_inferior_exit): Use inferior's exit
	code fields.
	* python/py-exitedevent.c (create_exited_event_object): Change
	type of 'exit_code'.  Optionally add exit_code attribute.
	(emit_exited_event): Change type of 'exit_code'.
	* python/py-event.h (emit_exited_event): Update.
	* mi/mi-interp.c (mi_inferior_exit): Print exit code.
	* infrun.c (handle_inferior_event): Set exit code fields on
	inferior.
	* inferior.h (struct inferior) <has_exit_code, exit_code>: New
	fields.
	* inferior.c (exit_inferior_1): Initialize new fields.
gdb/doc
	* gdb.texinfo (GDB/MI Async Records): Document 'exit-code' field.
	(Events In Python): Note that exit_code is optional.