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

[Andrew Haley]

Ralph Loader writes:
 > > I was wondering about a similar thing in kaffe, and it may be saner to 
 > > write the array index argument checking code once in a final class in 
 > > Java and/or a static inline method in C++/function in C and let the 
 > > compiler do the inlining magic.
 > 
 > Sounds good in theory.  A couple of issues to deal with in practice:
 > 
 > - sometimes you have start and length, sometimes you have start and
 > end.  The APIs aren't consistent.
 > 
 > - how good is the java compiler at inlining?

These days it's pretty good, but the bounds checks are done in C++.
Its inliner is pretty good too.

Andrew.