This is a big step towards a cleaner api. The struct reference in
model_t really should be a pointer, but bsp submodel(?) loading messed
that up, though that's just a matter of taking more care in the loading
code. It seems sensible to make that a separate step.
I got rather tired of there being multiple definitions of mostly compatible
plane types (and I need a common type anyway). dplane_t still exists for
now because I want to be careful when messing with the actual bsp format.
When R_AddEfrags is used (as is the case in nq), this function is
redundant. Brush models in qw are currently broken (invisible), but that's
just a matter of getting qw to use R_AddEfrags instead of R_NewEntity.
This removal should speed up the software renderers a little bit.
a static `stack') to avoid the function call overhead. this cuts about 40%
of the execution time from this function.
No matter what I tried, best results were obtained using __builtin_expect,
so make sure non-gcc compilers do the right thing when they encounter it.
