What changed in EDuke32, build by build

* The current setup that's been long-standing has the player come to a complete stand-still for one tic while transiting through a portal. * By saving off the velocity difference between the player's pos/opos, we can re-apply that to opos to make the portal transition truly seamless.

Fixes a bug where an empty filename is interpreted as the current directory "./", which of course always exists.

The rationale here is that it's better to provide the build instructions for these libraries (as we already do) with no binary than it is to provide outdated binaries that don't actually match the provided headers anymore.

We were only using this to make clang behave like GCC, but some versions of GCC are bugged such that enabling -frounding-math prevents them from correctly handling constexpr float values determined at compile time.

-Missing mip levels are now drawn by scaling the highest mip level present in the file, not just taking mip 0 when e.g we want mip 4 but 0-3 are available -Algorithm for determining which mip level to use has been adjusted to bias for rendering quality and not just speed (e.g don't display the chunkier mip levels at such close distances) -Mip levels other than the default are now run through a conversion process that standardizes the colors used based on those found in mip 0, to work around issues where the mip levels ended up with fullbright colors substituted in place of regular palette entries when the mips were originally generated by SLABSPRI/SLAB6 -Add terrible heuristic for mip level rejection based on how many visible voxels are present in the higher mip level versus the lower mip levels for the same voxel. This is intended to work around issues where SLABSPRI and SLAB6 both generated their mips by removing cubes a bit too liberally, resulting in any feature of the model that was only 1 voxel thick being completely obliterated by the mip generation process. This can be observed by setting r_novoxmips to 0 in older builds and viewing 8756_FLOORLAMP_ON.kvx from Ion Fury 2.0 or earlier at various distances in-game. Without this heuristic, poorly generated mip levels that end up obliterating the entire lampshade are drawn.

Not particularly exciting or useful now that the converted versions are cached.

Fixes textures with fullbright pixels being drawn completely bright when texture filtering is enabled, and a couple other issues.

Benefits: almost 200 lines deleted from the Makefile, new source files added to the project require no additional setup. Drawback: you can't leave random shit with .c or .cpp file extensions laying around your source directories (sounds more like another benefit tbh).

Something somewhere is still fucked, though (and was before this commit)