Big wxDataViewCtrl renderer classes refactoring.

Big wxDataViewCtrl renderer classes refactoring.

This commit adds no changes in functionality but paves way for the upcoming
improvements of wxDataViewCustomRenderer.

First, introduce wxDataViewCustomRendererBase class in order to allow
implementing behaviour common to custom renderers in all ports in this class
instead of triplicating it.

This required splitting monolithic dataview.h in more parts, now we have
wx/dvrenderer.h which defines wxDataViewRendererBase and the new
wxDataViewCustomRendererBase and includes wx/port/dvrenderer.h which define
wxDataViewRenderer and wx/port/dvrenderers.h which defines all the other
renderer classes.

Also bring renderers hierarchy in the generic version closer to other ports:
all standard renderer classes now inherit from wxDataViewRenderer and not
wxDataViewCustomRenderer in for consistency with the other ports.
wxDataViewRenderer itself still does derive from wxDataViewCustomRendererBase,
unlike elsewhere, but this is unavoidable considering that all generic
renderers are custom ones.

Finally do some cleanup in OS X part of the code: correct indentation,
spacing, comment style.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@62589 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775