[Bug libstdc++/64657] New: Support iterators with overloaded operator-comma

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64657

            Bug ID: 64657
           Summary: Support iterators with overloaded operator-comma
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Keywords: rejects-valid
          Severity: minor
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org

It's not possible to use several libstdc++ algorithms with iterators that have
overloaded comma operators, due to expressions like:

  ++__beg, ++__pos;