ntdll: rtlstr.c: Implement checking for control characters in RtlIsTextUnicode [try 2]

[Zac Brown]

Dan Kegel wrote:
> The array doesn't make much sense if you're not going to iterate over it.
> It might be more readable if you replaced the array and long if
> with a switch statement.
> It would be nice to break out of the loop early.
> The last two suggestions together kind of mean a goto, which is ugly,
> but not too uncommon in wine.
> (You might want to verify that the generated code isn't too slow,
> but since len is limited to 256, that probably doesn't matter.)
> 
> e.g.
> 
>     if (flags & IS_TEXT_UNICODE_CONTROLS)
> 	for (i = 0; i < len; i++)
>            switch (s[i]) {
>            case '\t':
>            case '\n':
>            case 'r':
>            case 0x20:
>                 out_flags |= IS_TEXT_UNICODE_CONTROLS;
>                 goto done;
>            default:
>            }
>     }
>     done:

I had thought about that before and initially wasn't sure of AJ's feelings on 
not declaring something that (I thought) might be considered magic values.

Now that I realized it needs to be optimized, I'll definitely look into it.

-Zac