Re: psql - add ability to test whether a variable exists

I was able to test the functionality (which seemed to work fine) and fed in my comment to assist anyone else reviewing this patch (and intentionally let it's state as 'Needs Review').

While trying to provide my feedback, on hindsight I should have been more detailed about what I didn't test. Being my first review, I didn't understand that not checking a box meant 'failure'. For e.g. I read the sgml changes, which felt okay but didn't click 'Passed' because my env wasn't setup properly.

I've set this back to 'Needs Review' because clearly needs it.
Apologies for the noise here.

The new status of this patch is: Needs review