They're now qfv_* and shared within the vulkan renderer. qfv_z_up cannot
be shared across renderers as they have their own ideas for the world
frame. qfv_box_rotations currently can't be shared across renderers
because if the Y-axis flip and the way it's handled, but sharing should
be achievable by modifying the other renderers to handle the sides
correctly (glsl and gl need to do lookups for the side enums, sw just
needs to be shown which way is up).
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).
