PR rtl-optimization/36419
	* combine-stack-adj.c (adjust_frame_related_expr): New function.
	(combine_stack_adjustments_for_block): Call it if needed.  Delete
	correct insn.
	* dwarf2out.c (dwarf2out_frame_debug_expr): Adjust
	DW_CFA_GNU_args_size if CSA pass merged some adjustments into
	prologue sp adjustment.

	* g++.dg/eh/async-unwind1.C: New test.

From-SVN: r137689