Refactor dominance.c: define dom_info as C++ class

Refactor dominance.c: define dom_info as C++ class

gcc/
	* dominance.c (new_zero_array): Define.
	(dom_info): Redefine as class with proper encapsulation.
	(dom_info::m_n_basic_blocks, m_reverse, m_start_block, m_end_block):
	Add new members.
	(dom_info::dom_info, ~dom_info): Define.  Use new/delete for memory
	allocations/deallocations.  Pass function as parameter (instead of
	using cfun).
	(dom_info::get_idom): Define accessor method.
	(dom_info::calc_dfs_tree_nonrec, calc_dfs_tree, compress, eval,
	link_roots, calc_idoms): Redefine as class members.  Do not use cfun.
	(calculate_dominance_info): Adjust to use dom_info class.
	(verify_dominators): Likewise.

From-SVN: r227093