[Patch] natString.cc: Some fixes for bounds checking arithmetic.

[Ralph Loader]

> Do you get a warning because String.getBytes is deprecated?

Yes.

> There's no way to change the options for just one file.  But we
> should probably run the test suite with -Wno-deprecated anyway --
> that should be easy to change in lang.exp.

Sounds good.

> 
> I wonder if these tests should go in Mauve instead.  Then they'll be
> shared with other free VMs.
> 
> Tom
>