- Rewrite wxHeaderCtrl to be virtual-like: even if we don't need an infinite

- Rewrite wxHeaderCtrl to be virtual-like: even if we don't need an infinite
  number of columns in it, it turns out that getting column information from
  the associated control is much easier than copying it into the control.
- Provide wxHeaderCtrlSimple derived class which can be used easily if
  callback approach of wxHeaderCtrl is not needed.
- Because of wxHeaderCtrl virtualization, port-specific implementations of
  wxHeaderColumn are not needed any more and were removed.
- Use wxHeaderCtrl in the generic wxDataViewCtrl: this means that column
  events are broken right now in it as they haven't been implemented by
  wxHeaderCtrl yet, this will be fixed a.s.a.p.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@57161 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775