FramebufferManager: Copy all EFB layers to the XFB framebuffer.
OGL: Support stereoscopic XFB blit to screen.
FramebufferManagerBase: Only allocate one layer for Real XFB.
GeometryShaderCache: Cosmetics.
FramebufferManager: Copy all EFB layers to the XFB.
D3D: Support stereoscopic XFB blit to screen.
VideoConfig: Turn off stereoscopy when Real XFB is enabled.
D3D: Remove obsolete Real XFB codepath.
FramebufferManager: Return framebuffer target size in GetTargetSize().
FramebufferManagerBase: Remove obsolete parameters.
Renderer: Use old method of calculating the source rectangle.
XFBEncoder: Sample the first layer of the resolved EFB texture.

Using the multisampled EFB texture is invalid, as the XFB encoder does not have a multisampling shader.
Merge pull request #1740 from Armada651/stereo-xfb

Support stereoscopy with Virtual XFB