Preparing to use shifts to eliminate redundant test/compare insns on H8

Preparing to use shifts to eliminate redundant test/compare insns on H8

	* config/h8300/h8300-protos.h (output_a_shift): Make first argument
	an array of rtx rather than a pointer to rtx.  Add code argument.
	(compute_a_shift_length): Similarly.
	* config/h8300/h8300.c (h8300_shift_costs): Adjust now that the
	shift itself isn't an operand.  Create dummy operand[0] to carry
	a mode and pass a suitable rtx code to compute_a_shift_length.
	(get_shift_alg): Adjust operand number of clobber in output templates.
	(output_a_shift): Make first argument an array of rtx rather than
	a pointer to rtx.  Add code argument for the type of shift.
	Adjust now that the shift itself is no longer an operand.
	(compute_a_shift_length): Similarly.
	* config/h8300/shiftrotate.md (shiftqi, shifthi, shiftsi): Use an
	iterator rather than nshift_operator.
	(shiftqi_noscratch, shifthi_noscratch, shiftsi_noscratch): Likewise.
	(shiftqi_clobber_flags): Adjust to API changes in output_a_shift
	and compute_a_shift_length.
	(shiftqi_noscratch_clobber_flags): Likewise.
	(shifthi_noscratch_clobber_flags): Likewise.
	(shiftsi_noscratch_clobber_flags): Likewise.