Clarify some behaviour in comments
Add a workaround for GLib < 2.33.1

I wanted to have it working in Wheezy and this was standing in the way,
so I went for the quick fix that I'd made available to myself.
Add a querying tool for use in e.g. IRC bots

Now the tools don't get built on `make all' but instead have their
own target called `tools'.  It might be reasonable to move them into
their own directory sometime, instead of cluttering `src'.