This moves the common camera setup code out of the individual drivers,
and completely removes vup/vright/vpn from the non-software renderers.
This has highlighted the craziness around AngleVectors with it putting
+X forward, -Y right and +Z up. The main issue with this is it requires
a 90 degree pre-rotation about the Z axis to get the camera pointing in
the right direction, and that's for the native sw renderer (vulkan needs
a 90 degree pre-rotation about X, and gl and glsl need to invert an
axis, too), though at least it's just a matrix swizzle and vector
negation. However, it does mean the camera matrices can't be used
directly.
Also rename vpn to vfwd (still abbreviated, but fwd is much clearer in
meaning (to me, at least) than pn (plane normal, I guess, but which
way?)).
So far, in gl and glsl, but viewposition is much clearer than r_origin
(despite being the same thing), and modelorg is just confusing (I think
it's the view position relative to the current model).
r_screen because of SCR_UpdateScreen, and r_cvar because the cvars
really should never have been in a plugin in the first place (and
r_screen needed access).
It turns out glsl, sw and sw32 weren't getting any benefit from R_CullBox
because the frustum wasn't setup :P. Get another 8% out of bigass1
(174->184fps). bigass1 now runs 2x as fast as it did before I started this
optimisation run :)
Where possible, symbols have been made static, prefixed with gl_/GL_ or
moved into the code shared by all renderers. This will make doing plugins
easier but done now for link testing.
Also some small cleanups in particles.
Brighten grenade smoke a tiny bit, so it's not so invisible in the typically dark quake areas.
And some minor cleanups to water rendering.
