Instruction panel: restructure information?

[gsalzer]

• Usually, in assembler listings, the first column is the address of the instruction in hex, starting with 0x0, and the second column is the mnemonic code of the instruction. If the instruction has arguments, they are appended to the mnemonic code and do not occupy additional lines.
  
• The mnemonic code INVALID is actually a valid instruction with opcode 0xfe. For undefined opcodes it would be better to choose e.g. MISSING with the opcode as an argument, like:
  
• The gas column could be made more narrow, if space is needed.
• If desired, the hex opcode could be added as an extra column, maybe followed by the arguments.
• The PC value should also be displayed in hex, to match the address column and the format of the jump addresses pushed on the stack.