* avr-dis.c (avr_operand): Use PARAMS macro in declaration.

	* avr-dis.c (avr_operand): Use PARAMS macro in declaration.
	Change return type from void to int.  Check the combination
	of operands, return 1 if valid.  Fix to avoid BUF overflow.
	Report undefined combinations of operands in COMMENT.
	Report internal errors to stderr.  Output the adiw/sbiw
	constant operand in both decimal and hex.
	(print_insn_avr): Disassemble ldd/std with displacement of 0
	as ld/st.  Check avr_operand () return value, handle invalid
	combinations of operands like unknown opcodes.