gtk: change GtkIconView to "support" actual trees
Remove the check for GTK_TREE_MODEL_LIST_ONLY and make the view display only the first level of the tree, ignoring all insert, remove etc. events on the model's branches. This enables generic application code which always produces GtkTreeStores (also for flat lists) to display grids of these flat trees.
Showing with 25 additions and 14 deletions