* cgraph.c (assembler_name_hash): New static var.
	(hash_node_by_assembler_name, eq_assembler_name): New.
	(cgraph_node_for_asm): Use hashtable.
	(cgraph_remove_node): Maintain hashtable.
	(change_decl_assembler_name): Sanity check that names are not changing
	after aliasing was processed.
	* cgraph.h (varpoon_node): Add next GGC marker.
	* tree.c (decl_assembler_name_equal): Constify.
	(decl_assembler_name_hash): New.
	* tree.h (decl_assembler_name_equal): Constify.
	(decl_assembler_name_hash): Update.

From-SVN: r137753