[PATCH] Change llvm-objdump to print (bad) for invalid instructions

[Rafael Espíndola]

> My thinking was that a unit test would test out-of-tree targets as well. If their disassemblers were copied from any of the in-tree targets, then they're almost certainly returning 0 bytes for invalid instructions. The unit test was designed to catch that (assuming the SubtargetInfo could be constructed from the architecture name alone).
>
> If that's not a concern or it's the wrong way to go about it, I can add tests for each in-tree target.

We normally use unit tests only when the issue is not easily visible
from one of the existing tools.

Cheers,
Rafael