3.24.2 operator +=

OEMolBase &operator+=(OEMolBase &lhs, const OEMolBase &rhs)
OEQMolBase &operator+=(OEQMolBase &lhs, const OEQMolBase &rhs)
OEQMol &operator+=(OEQMol &lhs, const OEQMol &rhs)
OEQMol &operator+=(OEQMol &lhs, const OEQMolBase &rhs)