[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 #11 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-04-12 10:14:15 UTC ---
Only in a few places in the associative, to instantiate _Rb_tree, but the
nested types are not used at all, afaics. And, well, if (in the near future) we
figure out some sort of nested types can be useful to have for such extensions,
we can still have with a different name.

So far the obvious patch appears to work pretty well. I'm completing
regtesting.