[v3] container requirements cleanups

[Paolo Carlini]

Benjamin Kosnik wrote:
> As part of this, I run into other bits of 41005, ie std::string::cbegin
> and friends. Corrected, but need to review the rest of this stuff.
>   
For the record, that was certainly on purpose: if you go through the
archive you will find a number of statements of mine to the effect that
since we would switch to a completely different implementation in C++0x
and the current one is also so intertwined with the rest of the *.so, we
would rather not experiment with the C++0x features, eg, I decided not
to add move constructor and assignment. Lately Jason "broke" that with
initializer_list things, I pointed out the reasoning, but was too
late... Really, if at all possible, let's not overload the refcounted
implementation.

Paolo.