The node struct was 72 bytes thus two cache line. Moving the pointer
into the brush model data block allows nodes to fit in a single cache
line (not that they're aligned yet, but that's next). It doesn't seem to
have made any difference to performance (at least in the vulkan
renderer), but it hasn't hurt, either, as the only place that needed the
parent pointer was R_MarkLeaves.
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.
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.
If the map got reloaded but the current leaf didn't change the world (and
most entities) didn't get drawn. Forcing a vis update by first setting
r_viewleaf to null and marking surfaces does the trick :)
