Machine code routine call instructions (`0NNN`) are not supported

[64kramsystem]

CHIP-8 has an instruction for invoking machine code routines (opcode 0NNN).

They're corrently not supported - when they're found, a decimal number is printed instead; while it can be understood, it's not in line with the overall disassembler functionality.

See, for example https://github.com/JohnEarnest/chip8Archive/blob/master/roms/mondrian.ch8, which starts with the common hires call (0x00FF).