a volatile method that can be overridden by
subclasses to take drawing control of tree item's content.
This replaces the old "item_draw_callback()" technique
added a few months ago as an ABI feature; turned out the
new technique is a better way to go.
o The examples/tree-custom-draw-items.cxx demo adjusted
accordingly.
o Added missing docs for some methods that had none,
including label_[xywh]().
o Added related methods needed to implement this, including:
Fl_Tree_Item_Array::replace()
Fl_Tree_Item::replace()
Fl_Tree::root(item)
Fl_Tree::add() variations
Fl_Tree_Item::drawbgcolor()/drawfgcolor()
o Carefully worked the FLTK_ABI_VERSION macros so as to be
ABI compatible with 1.3.0.
o Verified 1.3.0 ABI compatibility with ABI Compliance Checker 1.99.8.5:
http://ispras.linuxbase.org/index.php/ABI_compliance_checker
git-svn-id: file:///fltk/svn/fltk/branches/branch-1.3@10071 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
o Added examples/tree-custom-draw-items.cxx to demonstrate its use.
o Fixed small doc error for recent Fl_Tree::get_selected_items()
git-svn-id: file:///fltk/svn/fltk/branches/branch-1.3@10018 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
