After installing JDeveloper 11.1.1.6.0 on 64-bit Ubuntu 12.04, it refuses to start. It says it can't find `libxext.so.6`. I can see that `libxext.so.6` does exist on the machine. Making a symlink to it in JDeveloper's own lib directory doesn't work because it's a 64-bit library, and JDeveloper is set up as 32-bit. How can we get the needed library installed so JDeveloper can run?