[v3] basic_string::reserve() shrink-to-fit?

[Paolo Carlini]

Neil Ferguson wrote:

> I haven't written a test case that specifically exercises my change,
> though, as I haven't had time to learn how yet. This is the first time
> I've meddled with libstdc++ :-)

Eh! By the way one of my very first patches also involved reserve, if
you are curious:

    http://gcc.gnu.org/ml/libstdc++/2001-11/msg00150.html

Your change looks good, let's wait a bit for Nathan's comments: if he
doesn't object, I will take care of the thing.

Paolo.