IPA REF alias refactoring

IPA REF alias refactoring

	* cgraph.h (iterate_direct_aliases): New function.
	(FOR_EACH_ALIAS): New macro iterates all direct aliases for a node.
	* cgraph.c (cgraph_for_node_thunks_and_aliases): Usage of
	FOR_EACH_ALIAS added.
	(cgraph_for_node_and_aliases): Likewise.
	* cgraphunit.c (assemble_thunks_and_aliases): Likewise.
	* ipa-inline.c (reset_edge_caches): Likewise.
	(update_caller_keys): Likewise.
	* trans-mem.c (ipa_tm_execute): Likewise.
	*varpool.c (varpool_analyze_node): Likewise.
	(varpool_for_node_and_aliases): Likewise.
	* ipa-ref.h (first_alias): New function.
	(last_alias): Likewise.
	(has_aliases_p): Likewise.
	* ipa-ref.c (ipa_ref::remove_reference): Removal function
	is sensitive to IPA_REF_ALIASes.
	* symtab.c (symtab_node::add_reference): Node of IPA_REF_ALIAS type
	are put at the beginning of the list.
	(symtab_node::iterate_direct_aliases): New function.

	* lto-partition.c (add_symbol_to_partition_1): Usage of
	FOR_EACH_ALIAS added.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@212191 138bc75d-0d04-0410-961f-82ee72b054a4