[patch lto/c++/middle-end/windows]: Fix handling of dllexport for LTO as externally_visible

[Jan Hubicka]

> 2010/11/16 Jan Hubicka <hubicka@ucw.cz>:
> > You need to only update cgraph_externally_visible_p and
> > varpool_externally_visible_p in ipa.c and
> > process_function_and_variable_attributes (that one is missing in your patch and
> > I think it is needed to solve same scenarios as
> > process_function_and_variable_attributes was introduced for).
> >
> > You would need to check the flag on all those places, too and attribute lookup
> > should be cheap given that those functions are called constant amount of times
> > per symbol.
> >
> > Honza
> >
> >
> 
> So here the version using dllexport attribute checking. Testcase as
> provided by prior patch.
> 
> Ok for apply?
OK, thanks!
Honza