X Border Attributes

XComposite, which is currently our only capture method for windows, doesn't handle X border width. This works in a lot of cases but anytime there's a border, a bug occurs where the lower right is clipped. 
This patch has two goals: 

1) To position and size the capture texture correctly in accordance to the border.
2) Adds a configuration option to allow people to toggle it (which in most cases will simply do nothing) with a default of not including it. 

Connected bugs: https://obsproject.com/mantis/view.php?id=62
Feel free to make another commit that removes that variable or moves it to the top or whatever, but please don't do it in this commit