Update unarm to 2.0

[AetiasHax]

I recently rewrote unarm to address several issues with it. The noteworthy effects on objdiff are:

• Vastly reduced code size and compilation time
• VFPv2 support (floating-point instructions, notably used by 3DS games)
• Less code in arm.rs, more things are handled by unarm now
  • No more combining 4-byte Thumb instructions manually
  • No more formatting other than deciding how arguments are converted into InstructionParts
• Slight performance difference
  • Parsing an instruction is slower due to additional correctness checks (ARM version, extensions, illegal values etc.)
  • Formatting instructions is faster due to fewer loops/branches and better use of traits
  • All in all, a small but not so noticeable performance loss

[encounter]

This shaves off ~0.5MB from the binary size, impressive! And a much cleaner arm.rs. Thanks!