* docs/papers/HackingOnThunar.odt: Improve the "Hacking on Thunar"
	  guide.
	* thunar-vfs/thunar-vfs-volume.{c,h}: Change the icon lookup mechanism
	  to return an icon name instead of a GtkIconInfo object. Also allow
	  the ThunarVfsVolume implementation to specify a custom icon by
	  overriding the lookup_icon_name() method. Add a new method
	  get_free_space() which can be used to determine the amount of free
	  space on a given volume.
	* thunar-vfs/thunar-vfs-volume-bsd.c: Catch up with the changes to
	  ThunarVfsVolume.
	* thunar/thunar-favourites-model.c: Cache icons for the favourites and
	  reload them whenever the file/volume changes. Adopt the new icon
	  lookup mechanism for ThunarVfsVolume.




(Old svn revision: 16388)