linux-capture: Add X border option to xcomposite

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.