desktop entry/launcher drag'n'drop

[Brian J. Tarricone]

hi all-

i started looking into DnD support for the xfdesktop menu.  the plan is 
to be able to drag an item from the menu out onto the panel (or later, 
the desktop itself).  but before this can work, the panel and xfdesktop 
need to agree on a SelectionData format, target/mime type, etc.  this is 
the first time i've messed with DnD, so if anyone knows The One Right 
Way To Do It, feel free to make suggestions, otherwise i'm going to 
make it up as i go along ^_~.

	-brian