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

[Tom Tromey]

>>>>> "Dalibor" == Dalibor Topic <robilad@kaffe.org> writes:

Dalibor> this kind of optimizations is pretty much the thing I hoped would be
Dalibor> easy to come up with, test and implement with my 'bounds checking api'
Dalibor> idea. thanks! ;)

I like this idea for C++ code.  For java code, making a static helper
method is a problem, because we will end up trying class
initialization for every call.

Tom