Convert remaining uses of value_range in ipa-*.cc to Value_Range.

Convert remaining uses of value_range in ipa-*.cc to Value_Range.

Minor cleanups to get rid of value_range in IPA.  There's only one left,
but it's in the switch code which is integer specific.

gcc/ChangeLog:

	* ipa-cp.cc (decide_whether_version_node): Adjust comment.
	* ipa-fnsummary.cc (evaluate_conditions_for_known_args): Adjust
	for Value_Range.
	(set_switch_stmt_execution_predicate): Same.
	* ipa-prop.cc (ipa_compute_jump_functions_for_edge): Same.