[C++-sig] preventing a copy of the vector when using the vector_indexing_suite

[Scott McKay]

>  Sorry about my ignorance. Why do you define those implicitly convertble
> pointers? 

It's required to make smart pointers work correctly to convert between
classes in the same hierarchy I believe.

There may be a cleaner implicit way to make them work, but this is the
approach I took after reading through old postings, faqs and various
boost::python/pyste doco.