(selected, mouse-over) and also optionally drawing the contents of the
header (label and/or bitmap, sort arrow) in a consistent way. Also
added a method to determine the default height of the column header.
This is based on work done for OSAF.
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@41201 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775