h8300-protos.h: Add prototypes for output_plussi, compute_plussi_length, and compute_plussi_cc.

	* config/h8300/h8300-protos.h: Add prototypes for
	output_plussi, compute_plussi_length, and compute_plussi_cc.
	* config/h8300/h8300.c (output_plussi): New.
	(compute_plussi_length): Likewise.
	(compute_plussi_cc): Likewise.
	* config/h8300/h8300.md (addsi_h8300h): Call
	output_plussi, compute_plussi_length, and compute_plussi_cc.

From-SVN: r60500