[v3] container requirements cleanups

[Jonathan Wakely]

2009/8/25 Benjamin Kosnik:
>
> Consistent application of 23 containers requirements checking.
>
> 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.

std::string and vstring are both missing shrink_to_fit() as well, I
have a patch for that which I'll send after I commit the 41005 fixes.

Jonathan