[C++0x] fix libstdc++/41005 - missing fstream instantiations

[Benjamin Kosnik]

> We already compile src/string-inst.cc and src/wstring-inst.cc with
> -std=gnu0x so that the new members are instantiated in the library,
> this does the same for fstream-inst.cc.
> 
>         PR libstdc++/41005
>         * src/Makefile.am (fstream-inst.o): Compile as C++0x.
>         * src/Makefile.in: Regenerate.
>         * config/abi/pre/gnu.ver: Add new exports and adjust old ones
> to be more precise.
> 
> The linker script changes are necessary so that the new symbols are
> not matched by the patterns in the 3.4 version.  Tested x86_64/linux,
> OK for trunk?

Yes.
 
> And 4.4 branch when I've tested it there?

Yes, but do an audit first on trunk to make sure that all the *-inst.cc
files that have C++0x MF's are done? Ideally there would be some link
tests for these.
 
> How would I add the symbols to the 4.4 linker map?  Would the fstream
> ones go in 3.4.13 and then the <future> symbols on trunk get moved to
> a new 3.4.14 version?

Yes.

-benjamin