Class GXLGXL lacks xlink namespace definition

This error only seems to occur in java1.5. The 1.4.x
versions don't seem to be troubled. The constructors in
class GXLGXL miss to set the coresponding attribute.
I've added:

this.setAttribute("xmlns:xlink","http://www.w3.org/1999/xlink");

To the constructors of GXLGXL. This seems to solve the
problem.