This doesn't work as expected in some cases, as surfaces might still get
linked transitively by neighbours. Solving this seems non-trivial for
now, but maybe we can just live with it
Automatically smooth normals between surfaces with normals less than 45
degrees off.
Can be adjusted from map.bsp.patch file like this (e.g. to 50 degrees):
```
{
"_xvk_smoothing_threshold" "50"
}
```
That PR has more stuff in it which we decided to drop.
This commit only contains:
- Detection of func_wall models, and adding their lights as static
(fixes#415).
- Patching func_wall models offsets, #335. Does not yet patch them
visually, but patches their light sources. Will be addressed in next
commits. Patching is done via model name, not entity id, also will be
fixed.
- Does not address culling (#118). This is the part dropped from the PR.
Needs different approach. TBD
