Add pretty printers for iterators of boost::intrusive::set and boost::intrusive::list. Pretty printers for intrusive set/list now checks whether there is a member variable that contains the size. If so it is printed by to_string(). Cleaned up some overly complex code for calculating the member hook offset.
Merge pull request #3 from johanst/intrusive

Boost.Intrusive improvements.
Merge branch 'intrusive'
Merge remote-tracking branch 'upstream/master'