Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Make it possible to use the debug versions of std::map and std::multimap
with clang, by removing two unneeded using declarations. Otherwise, you
would get errors similar to:

/usr/include/c++/4.2/debug/map.h:77:20: error: dependent using declaration resolved to type without 'typename'
using _Base::value_compare;
^

N.B.: Take care when you actually use the debug versions of any
libstdc++ header. They are more likely to contain problems, because
they are exercised far less often, and since the standard library
complexity guarantees don't always apply anymore, compile times can
drastically increase.

MFC after: 2 weeks

This commit was generated by cvs2svn to compensate for changes in r169691,
which included commits to RCS files with non-trunk default branches.

GCC 4.2.0 release C++ standard library and runtime support code.

Gcc 3.4.4 C++ support bits.

Gcc 3.4.2 20040728 C++ support bits.