resource.c: Use rtx_sequence

resource.c: Use rtx_sequence

gcc/
2014-08-27  David Malcolm  <dmalcolm@redhat.com>

	* resource.c (mark_referenced_resources): Strengthen local
	"sequence" from rtx to rtx_sequence *, adding a checked cast, and
	using methods of rtx_sequence to clarify the code.
	(find_dead_or_set_registers): Within the switch statement, convert
	a GET_CODE check to a dyn_cast, introducing local "seq".  Within
	the JUMP_P handling, introduce another local "seq", adding a
	checked cast to rtx_sequence *.  In both cases, use methods of
	rtx_sequence to clarify the code.
	(mark_set_resources): Within SEQUENCE case, introduce local "seq"
	via a checked cast, and use methods of rtx_sequence to simplify
	the code.

From-SVN: r214598