ext/vstring.h swap vs unequal allocators

[Paolo Carlini]

Hi all, Howard,

I'm reading in detail Issue 431 and therefore N1599 and I'm thinking of
implementing Option 3 for our ext/vstring framework. Basically, would
mean removing the O(N) fallback and replacing it with a swap of the
allocators. Also, I'm wondering whether that would not be appropriate
also for our current basic_string...

Have yet to audit the containers proper, but likely most are already
implementing Option 3. Will do...

Any comments?

Paolo.