* basic_block.h (struct basic_block_def): Added prev_bb and next_bb
	fields.
	(FOR_BB_BETWEEN, FOR_ALL_BB, FOR_ALL_BB_REVERSE): New macros for
	traversing basic block chain.
	(create_basic_block_structure, create_basic_block): Declaration changed.
	(link_block, unlink_block): Declare.
	* cfg.c (entry_exit_blocks): Initialize new fields.
	(link_block, unlink_block): New.
	(expunge_block_nocompact): Unlink basic block.
	(dump_flow_info): Print prev_bb/next_bb fields.
	* cfgbuild.c (find_basic_blocks_1, find_basic_blocks): Modified.
	* cfgcleanup.c (merge_blocks_move_predecessor_nojumps): Modified.
	* cfglayout.c (fixup_reorder_chain, cfg_layout_duplicate_bb): Modified.
	* cfgrtl.c (create_basic_block_structure, create_basic_block,
	split_block, force_nonfallthru_and_redirect, split_edge): Modified.
	(verify_flow_info): Check that list agrees with numbering.

From-SVN: r53642