[Bug libstdc++/65754] [5/6 Regression] missing exports for fstream constructors

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65754

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Patch posted to https://gcc.gnu.org/ml/gcc-patches/2015-04/msg00605.html