Don't use PyLong_FromLongLong

This changes gdb to avoid PyLong_FromLongLong, preferring to use
gdb_py_object_from_longest instead.

gdb/ChangeLog
2020-09-15  Tom Tromey  <tromey@adacore.com>

	* python/py-infevents.c (create_register_changed_event_object):
	Use gdb_py_object_from_longest.
	* python/py-exitedevent.c (create_exited_event_object): Use
	gdb_py_object_from_longest.