XFBEncoder: Cosmetics.
D3D: Fix Virtual XFB viewport.

Looks like I was incorrect about swapping the bottom and top members.
Renderer: Invalidate the FramebufferManager if the XFB mode is changed.

Fixes incorrect texture sizes after switching XFB modes.
Renderer: Cosmetics.
Merge pull request #1781 from Armada651/xfb-fixes

D3D: Fix Virtual XFB viewport.