Remove first_pass_instance from pass_dominator

Remove first_pass_instance from pass_dominator

2015-11-16  Tom de Vries  <tom@codesourcery.com>

	* passes.def: Add arg to pass_dominator pass instantiation.
	* tree-pass.h (first_pass_instance): Remove pass_dominator-related bit
	of comment.
	* tree-ssa-dom.c (pass_dominator::pass_dominator): Initialize
	may_peel_loop_headers_p.
	(pass_dominator::set_pass_param): New member function.  Set
	may_peel_loop_headers_p.
	(pass_dominator::may_peel_loop_headers_p): New private member.
	(pass_dominator::execute): Use may_peel_loop_headers_p instead of
	first_pass_instance.

From-SVN: r230417