We use attributeless rendering, so officially we have to bind _any_ VAO.
As the state of this VAO doesn't matter, we don't have to switch it.
Also fix an AMD issue as they don't like to render from an empty VAO.
We neither scale nor render from subimages, so we by using gl_Position, we don't have to generate _any_ vertices for this converting.
Also remove the glTexSubImage optimization as every driver does it when needed. But there are some workflows (eg on APU) where it's better to realloc this texture instead of a second memcpy or stall.
This fixes Real XFB Jaggies in OpenGL on games which use yscaling, such
as most PAL games.
This fixes the last of the "Real XFB Macroblocking" issues for opengl,
see issue #6503
Seems OpenGL ES 3 Requires you must have an lod argument, while Desktop
versions require you must not have a lod argument if you are using a
Sampler2DRect (which doesn't do Mipmapping).
