reload.c (find_reloads): Emit USEs to mark where a pseudo is reloaced with the MEM of its stack slot.

	* reload.c (find_reloads): Emit USEs to mark where a pseudo
	is reloaced with the MEM of its stack slot.
	* reload1.c (cannot_omit_stores): Delete.
	(reload): Don't initialize it.
	Don't apply avoid_return_reg logic to USEs.
	When done, remove USEs that have a REG_EQUAL note on them.
	(emit_reload_insns): Handle case where we have inherited a MEM.
	(delete_output_reload): Don't use cannot_omit_stores.

From-SVN: r19508