Re: [boost] [safe_numerics] review

In fact, the promotion policy can be eliminated entirely if the underlying type is always made automatic.

Specifically, instead of the current arrangement where all user-visible templates resolve to safe_base, and assuming for a moment that we only support the range of intmax_t, we could have template class safe_range; as a basis and then define safe as safe_range. Unfortunately, due to the need to support uintmax_t, which doesn't fit in intmax_t, we'd need two safe_range types and support for mixed operations, which would complicate things a bit on the implementation side. On the user side though there'd be no need for promotion policies. Although operator~ would no longer be supportable. One would have to explicitly xor with ~0 (of the correct type.)