ipa-strub: Replace cgraph_node order with uid.

ipa-strub: Replace cgraph_node order with uid.

ipa_strub_set_mode_for_new_functions uses node order as unique ever
increasing identifier. This is better satisfied with uid.
Order loses uniqueness with following patches.

gcc/ChangeLog:
	* ipa-strub.cc (ipa_strub_set_mode_for_new_functions): Replace
	order with uid.
	(pass_ipa_strub_mode::execute): Likewise.