g++ 4.7 compile fix in vector11

With g++ 4.7, the following error occurs when trying to compile code that uses Vector11:

../OpenMesh/Core/Geometry/Vector11T.hh: In function ‘decltype ((_v1 % _v2)) OpenMesh::cross(const OpenMesh::VectorT<LScalar, DIM>&, const OpenMesh::VectorT<RScalar, DIM>&) [with LScalar = float; RScalar = float; int DIM = 3; decltype ((_v1 % _v2)) = OpenMesh::VectorT<float, 3>]’:
../OpenMesh/Core/Geometry/Vector11T.hh:89:19: error: ‘OpenMesh::VectorT<float, 3>::container OpenMesh::VectorT<float, 3>::values_’ is private

It looks like this version of g++ would not be able to deal with the decltype statement used when overriding the "%" operator, where the "this->values_" part is not working properly. This issue should be fixed with this merge request.