Move all global state data into opcode table struct, and treat

	Move all global state data into opcode table struct, and treat
	opcode table as something that is "opened/closed".
	* cgen.h (CGEN_OPCODE_DESC): New type.
	(all fns): New first arg of opcode table descriptor.
	(cgen_set_parse_operand_fn): Add prototype.
	(cgen_current_machine,cgen_current_endian): Delete.
	(CGEN_OPCODE_TABLE): New members mach,endian,operand_table,
	parse_operand_fn,asm_hash_table,asm_hash_table_entries,
	dis_hash_table,dis_hash_table_entries.
	(opcode_open,opcode_close): Add prototypes.

	* cgen.h (cgen_insn): New element `cdx'.