Add an option to make disassembly more forgiving

[feliam]

For consideration...

Added "silent" to disassemble_one, disassemble_all, disassemble so it returns an INVALID when undefined opcode or a zero completed operand when no more data in bytecode.

(Also it adds a copy.copy there. May be a bug not to do it because several disassemblies? will be using the same Instruction instance? )

[computerality]

Should this just get instruction_table[0xfe] for INVALID? Also is there something in the yellow paper that describes the behavior when an unimplemented instruction is run? Just want to make sure it's semantically the same as INVALID, but I don't see anything.

[feliam]

Opps I ment to get 0xfe.

Unimplemented instruction is defined in the yellow (if I remember correctly) as the same as an INVALID. Only diff is that it may get redefined I guess ..

[feliam]

    try:
        instruction = copy(instruction_table[opcode])
    except KeyError:
        if silent:
            instruction = copy(instruction_table[0xfe])
        else:
            raise

??