[llvm] r200606 - MC: Improve the .fill directive's compatibility with GAS

[Rafael Espíndola]

> +      unsigned EmissionSize = PowerOf2Floor(Remaining);
> +      if (EmissionSize > 4)
> +        EmissionSize = 4;

Why can't this be an assert(EmissionSize <= 4)?

Please also add a test showing the big endian behavior.

Cheers,
Rafael