Viewport and FOV updates are now separate so updating one doesn't cause
recalculations of the other. Also, perspective setup is now done
directly from the tangents of the half angles for fov_x and fov_y making
the renderers independent of fov/aspect mode. I imagine things are a bit
of a mess with view size changes, and especially screen size changes
(not supported yet anyway), and vulkan winds up updating its projection
matrices every frame, but everything that's expected to work does
(vulkan errors out for fisheye or warp due to frame buffer creation not
being supported yet).
Of course, it's not as correct as glsl or sw due to using polygons and
uvs rather than a fragment shader (not that such is out of the question
since GL 3.0 is requested, but I don't feel like getting shaders going
just for a couple of post-processing effects in an obsolete renderer).
