My first patch! (to \df output)

Hello Hackers!

So, currently the only way to see if a function is security definer or not is to directly query pg_proc. This is both irritating, and I think perhaps dangerous since security definer functions can be  so powerful. I thought that rectifying that would make an excellent first patch, and I was bored today here in Prague since pgconf.eu is now over...so here it is. :)

This patch adds a column to the output of \df titled "Security" with values of "definer" or "invoker" based on the boolean secdef column from pg_proc. I've also included a small doc patch to match. This patch is against master from git. Comments welcome!

I just realized I didn't address regression tests, so I guess this is not actually complete yet. I should have time for that next week after I get back to the states.

I would also like to start discussion about perhaps adding a couple more things to \df+, specifically function execution permissions (which are also exposed nowhere outside the catalog to my knowledge), and maybe search_path since that's related to secdef. Thoughts?

This was actually kind of anti-climactic, since it only took about 5 minutes to make the change and get it working. Didn't really feel the way I expected it to ;)