if-to-switch: remove memory leaks

if-to-switch: remove memory leaks

gcc/ChangeLog:

	* gimple-if-to-switch.cc (struct condition_info): Use auto_var.
	(if_chain::is_beneficial): Delete clusters
	(find_conditions): Make second argument of conditions_in_bbs a
	pointer so that we control over it's lifetime.
	(pass_if_to_switch::execute): Delete them.