Re: [boost] [xint] Fifth release -- one more round of reviews, please

A few more: integer_t constructors taking 'const charT *, charT **' don't compile, due to const correctness issues (assigning a charT const* to a charT*). convert.hpp line 140 works around it with const_cast, but the signature should just be changed to 'const charT *, const charT **' (or better yet 'const charT *, const charT *&', as previously mentioned). raw_integer line 131 & convert.hpp line 103, from_string takes char** rather than charT**. std::size_t should be used universally instead of size_t.