Libxfce4ui api review

[Nick Schermer]

Another function that might be useful is the create_item_icon()
function in the libxfce4menu test application [1]. I think we use that
in a bunch of places to handle the (sometimes) weird Icon= values in
desktop files. On the other hand I think we should ignore values that
are not icon-names or absolute locations.

Nick

[1] http://svn.xfce.org/svn/xfce/libxfce4menu/trunk/tests/test-display-menu.c