Use rtx_insn in more places in dwarf2cfi.c

Use rtx_insn in more places in dwarf2cfi.c

gcc/
2014-08-28  David Malcolm  <dmalcolm@redhat.com>

	* dwarf2cfi.c (dw_trace_info): Strengthen field "head" from rtx to
	rtx_insn *.
	(get_trace_info): Likewise for param "insn".
	(save_point_p): Likewise.
	(maybe_record_trace_start): Likewise for both params.
	(maybe_record_trace_start_abnormal): Likewise.
	(create_trace_edges): Likewise for sole param and for three of the
	locals named "lab".
	(scan_trace): Strengthen local "prev", "insn", "control" from rtx
	to rtx_insn *, and update a call to pat->element to pat->insn.

From-SVN: r214689