Minimize <iosfwd>

[Paolo Carlini]

Hi Zack,

>                === libstdc++ tests ===
> XPASS: 27_io/fpos/14320-1.cc execution test
>                === libstdc++ Summary ===
> # of expected passes            4223
> # of unexpected successes       1
> # of expected failures          28
> # of unsupported tests          316

in general, all those unsupported tests cannot be considered normal for 
the gnu locale model. Likely it's just matter of installing the required 
localedata, but given the kind of change, better be safe and make sure 
all the tests involving named locales actually pass.

Anyway, tomorrow, I will look a bit more into it myself, after 
committing my last patch.

Paolo.