* class.c (subobject_offset_fn): New type.
(dfs_record_base_offsets): Remove.
(record_base_offsets): Likewise.
(dfs_search_base_offsets): Likewise.
(record_subobject_offset): New function.
(check_subobject_offset): Likewise.
(walk_subobject_offsets): Likewise.
(record_subobject_offsets): Likewise.
(layout_conflict_p): Reimplement.
(layout_nonempty_base_or_field): Correct handling of type
conflicts during layout.
(layout_empty_base): Likewise.
(build_base_field): Adjust to handle new representation of empty
base offset table.
(build_base_fields): Likewise.
(layout_virtual_bases): Likewise.
(splay_tree_compare_integer_csts): New function.
(layout_class_type): Use a splay_tree, rather than a varray, to
represent the offsets of empty bases.