GE debugger - fix depth/stencil, pan/zoom the texture

The user interface may be non-obvious.  It makes sense to me, but I'm open to suggestions.  I suck at making icons.

Double clicking zooms the texture in to 1x (could also have a button, I suppose...)  Once you've zoomed in, you can also click and drag to pan the texture (or framebuffer) within the view.

Still no UI to toggle between the stencil, depth, and color buffers, but I've verified that it does return valid data now at least on NVIDIA.

Curiously, depth is not updated properly in Phantasy Star Portable.  I'm wondering if maybe it's supposed to be unsigned or something (softgpu, which works, seems to make all comparisons as unsigned.)  I'm gonna try that next...

-[Unknown]