Add explicit transfer annotations to gtk_icon_view_get_cursor

Add explicit transfer annotations to gtk_icon_view_get_cursor

The cell out argument to gtk_icon_view_get_cursor is a pass-through
for gtk_cell_area_get_focus_cell which is transfer none. Without
this explicit annotation, transfer full is defaulted and introspection
bindings will assume ownership of the GtkIconViews reference to the
cell, causing crashes. Additionally add explicit transfer full to
the path parameter because it is expected the caller will free the
returned memory.

https://bugzilla.gnome.org/show_bug.cgi?id=704700