-Wconversion versus libstdc++

[Paolo Carlini]

Hi Gerald,

>I noticed that -Wconversion now issues warnings in libstdc++.
>  
>
in a nutshell, what is happening is that a difference of two pointers is 
assigned to an unsigned variable. First blush, the warning seems to me a 
bit overzealous, but if we concur that this is what we *really* want for 
4.3, we can change the affected (very old, indeed) lines of code, no 
problem at all.

Thanks,
Paolo.