rsvg2: fix memory leak of Handle.new_from_data and .new_from_file
rsvg2: fix memory leak of Handle.new_from_data and .new_from_file

GitHub: fix #318

Reported by Kagetsuki. Thanks!!!

kitachro/ruby-gnome2,kitachro/ruby-gnome2,kitachro/ruby-gnome2,kitachro/ruby-gnome2,kitachro/ruby-gnome2