Show tabs for depth/stencil in ge debugger, other improvements

This:
 * Finally fixes the initial state of the preview frames (yay.)
 * Fixes some dragging issues in the previews.
 * Adds a feature to jump to a particular displaylist address in the viewer.
 * Shows a tab selector for color/depth/stencil buffer.

Now you can easily see the depth buffer.  Probably it could be visualized better.

-[Unknown]