dev/cleanup

I've gotten tired of digging around for GUI-related code dealing with callbacks and other magical glib/gtk things when trying to get webkit2 at least building, so I've put them all into one file. I haven't noticed any regressions with it (using a build of it to submit this), but wider testing would be good.

Further work on this branch will be cleaning up the commands.c and variables.c files, but I'm pushing it up piecemeal. As for the branches it conflicts with (pretty much all of mine I believe), I'll deal with them in whatever order they land (though it'd be nice if this landed earlier since rebasing them on top of this would be easier).

I'll try to split up the commit in the future, but I don't have the patience tonight. There are also some bug fixes scattered throughout. I'll try to make them separate commits when splitting.

In the process, I cleaned up the code a bit and standardized the style to something which seemed like what is dominant in the repository (I did move function open braces to their own line because I don't like the way it folds in Vim).