0.0.22
 - NEW: Bump gegl to 0.0.22
 - NEW: New major soversion (ABI breakage in gegl)
 - NEW: Gegl::Buffer::destroy()
 - NEW: Gegl::Buffer::linear_open()
 - NEW: Gegl::Buffer::linear_close()
 - NEW: Gegl::Node::add_child()
 - NEW: Gegl::Node::remove_child()
 - BUG: configure didn't enforce a gegl recent enough.
 - API: use the new operation names for gegl (ABI break)