generator and glibsharp changes from bindinator's GSoC work

I've reviewed/tweaked all commits from https://github.com/mono-soc-2013/gtk-sharp/commits/gsoc-xDarkice,
concentrating on style and removing unused things, clarifying some commits messages, and
avoiding unneeded API changes. This, combined to the review from @andreiagaita, should be enough to
be pushed upstream.