Add support to the ARC disassembler for selecting instruction classes.

gas	* testsuite/gas/arc/dsp.d: New file.
	* testsuite/gas/arc/dsp.s: Likewise.
	* testsuite/gas/arc/fpu.d: Likewise.
	* testsuite/gas/arc/fpu.s: Likewise.
	* testsuite/gas/arc/ext2op.d: Add specific disassembler option.
	* testsuite/gas/arc/ext3op.d: Likewise.
	* testsuite/gas/arc/tdpfp.d: Likewise.
	* testsuite/gas/arc/tfpuda.d: Likewise.

opcodes	* arc-dis.c (skipclass): New structure.
	(decodelist): New variable.
	(is_compatible_p): New function.
	(new_element): Likewise.
	(skip_class_p): Likewise.
	(find_format_from_table): Use skip_class_p function.
	(find_format): Decode first the extension instructions.
	(print_insn_arc): Select either ARCEM or ARCHS based on elf
	e_flags.
	(parse_option): New function.
	(parse_disassembler_options): Likewise.
	(print_arc_disassembler_options): Likewise.
	(print_insn_arc): Use parse_disassembler_options function.  Proper
	select ARCv2 cpu variant.
	* disassemble.c (disassembler_usage): Add ARC disassembler
	options.

binutils* doc/binutils.texi (objdump): Add ARC disassembler options.
	* testsuite/binutils-all/arc/dsp.s: New file.
	* testsuite/binutils-all/arc/objdump.exp: Likewise.

include	* dis-asm.h: Declare print_arc_disassembler_options.