[Bug libstdc++/52942] [4.7/4.8 Regression] using std::ref with a std::unordered_map fails to compile

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52942

--- Comment #9 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-04-12 
09:56:54 UTC ---
... or ;) in C++11 mode, have _Select1st and _Identity not deriving from
unary_function. Should work, very, very simple patch, and in any case the
latter is deprecated in C++11, we really want to see it around as little as
possible.