[Bug bootstrap/86739] [9 Regression] Bootstrap broken with host GCC 4.1.2

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86739

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Regressed between r262525 (good) and r262545 (bad).  Thus probably caused by
r262539.

/usr/include/c++/4.1.2/bits/stl_pair.h:84 is

      /** Two objects may be passed to a @c pair constructor to be copied.  */
      pair(const _T1& __a, const _T2& __b)
      : first(__a), second(__b) { }

so it somehow doesn't like _T1 == vec_usage*& here I added with

    std::pair<const Key&, Value&> operator* ()
    {
      hash_entry &e = *m_iter;
      return std::pair<const Key&, Value&> (e.m_key, e.m_value);
    }

C++ folks?