This is the first step towards component-based entities.
There's still some transform-related stuff in the struct that needs to
be moved, but it's all entirely client related (rather than renderer)
and will probably go into a "client" component. Also, the current
components are directly included structs rather than references as I
didn't want to deal with the object management at this stage.
As part of the process (because transforms use simd) this also starts
the process of moving QF to using simd for vectors and matrices. There's
now a mess of simd and sisd code mixed together, but it works
surprisingly well together.
This has several benifits:
o The silly issue with alias model pitches being backwards is kept out
of the renderer (it's a quakec thing: entites do their pitch
backwards, but originally, only alias models were rotated. Hipnotic
did brush entity rotations in the correct direction).
o Angle to frame vector conversions are done only when the entity's
angles vector changes, rather than every frame. This avoids a lot of
unnecessary trig function calls.
o Once transformed, an entity's frame vectors are always available.
However, the vectors are left handed rather than right handed (ie,
forward/left/up instead of forward/right/up): just a matter of
watching the sign. This avoids even more trig calls (flag models in
qw).
o This paves the way for merging brush entity surface rendering with the
world model surface rendering (the actual goal of this patch).
o This also paves the way for using quaternions to represent entity
orientation, as that would be a protocol change.
