Classlib: QPenPrinter: Add 'bounds' method

This PR makes it simpler to use the same function as a UserView drawFunc and also with QPenPrinter.

Use case: Say I want to print vector graphics from a user view. I test the drawFunc in a user view (easier to see the results immediately). I want the function to adapt to the view size, so the function begins:

    u.drawFunc = { |view|
    	var b = view.bounds.moveTo(0, 0);
    	...
    };

Now I've got it looking right, so I want to use it in QPenPrinter, but guess what? "Message 'bounds' not understood." So then I have to edit the function to call `pageRect` instead, or write something really silly like:

    var b = if(view.isKindOf(QPenPrinter)) {
    	view.pageRect
    } {
    	view.bounds
    }.moveTo(0, 0);

Since the QPenPrinter is basically a stand-in for the user view, I think it should also respond to `bounds`.