Ruby-GNOME-0.31 is out!

* General
- Add Copying file to each sub libraries.
- Fix a compiling problem with ruby-1.8.x
* Ruby/GTK
- Fix problems when Gtk.main_quit called in another thread.
- Fix segfaults of Font.load.
* Ruby/Libart: Add Art::Bpath, Art::Canvas, Art::SVP, Art::Vpath.