[PATCH] MC: handle ParseDirective properly

[Rafael Espíndola]

> Comment at: lib/Target/X86/AsmParser/X86AsmParser.cpp:2693
> @@ -2695,3 +2692,3 @@
>    } else {
> -    return Error(L, "unexpected directive " + IDVal);
> +    llvm_unreachable("unexpected directive " + IDVal);
>    }
> ----------------
> This should probably be an Error + return false since it can be reached with a broken .s

and llvm_unreachable takes a plain "const char*" :-)

Cheers,
Rafael