[RFA] Removing const from std::swap

[Paolo Carlini]

Hi everyone,

some time ago, in an overzealous (it seems ;) series of const- tweaks to
the algorithms, I touched std::swap too, adding a const to the temporary
__tmp:

  template<typename _Tp>
    inline void
    swap(_Tp& __a, _Tp& __b)
    {
      // concept requirements
      __glibcxx_function_requires(_SGIAssignableConcept<_Tp>)

      const _Tp __tmp = __a;
      __a = __b;
      __b = __tmp;
    }

This is strictly speaking absolutely legal, as the concept check also
demonstrates, but now people on the c++.moderated list, Howard Hinnant
for example, believe that this is "overly pedantic" ;) ... Shall I
remove it? If we keep it, auto_ptrs cannot be swapped, as an extension,
indeed...

Thanks,
Paolo.