[Patch] Fix seek to beg after grow bug

[Paolo Carlini]

>
>
>Maybe you are working with the code as it was before 169, and I am 
>imagining it as it must be after?
>
I think so ;)

Nathan, I agree completely with your picture (of course, you already 
started explaining it
to me privately!), but I'm not sure to be able to actually implement 
completely it in the near
future: it's a real revolution wrt the current situation (a bit of a 
mess in quite a few places, as
you concur now: 9404 is just the 'tip of the iceberg', as we say in Italy)

I'm going to commit this tiny fix for Peter's problem (the bulk of it, 
the testcases, are going
to remain useful in the future ;), then, I promise, in the time allowed 
by my paid work, I will
start implementing your framework under you guide (as we already did for 
that nice series of
performance/conformance improvements to the string class).

Thanks again,
Paolo.