gensupport.c (init_rtx_reader_args_cb): Start counting code generating patterns from 1 to free up 0 for CODE_FOR_nothing.

	* gensupport.c (init_rtx_reader_args_cb): Start counting code
	generating patterns from 1 to free up 0 for CODE_FOR_nothing.
	* gencodes.c (main): Give CODE_FOR_nothing the value 0.  Add
	the LAST_INSN_CODE marker at the end.
	* genoutput.c (nothing): New static struct data.
	(idata): Initialize to &nothing.
	(idata_end): Initialize to &nothing.next.
	(init_insn_for_nothing): New function to create dummy 'nothing' insn.
	(main): Use it.
	* genpeep.c (insn_code_number): Remove global variable.
	(gen_peephole): Take it as an argument instead.
	(main): Take insn_code_number from read_md_rtx.
	* optabs.h: Revert r161809:
	(optab_handlers): Change type of insn_code back to insn_code.
	(optab_handler, widening_optab_handler, set_optab_handler,
	set_widening_optab_handler, convert_optab_handler,
	set_convert_optab_handler, direct_optab_handler,
	set_direct_optab_handler): Remove int casts.
	Revert to treating the insn_code field as "insn_code".

From-SVN: r189366