All my work thus far on solving the drawflag/renderflag/additive/subtractive conundrum.
Outstandng problems:
* Bad additive/subtractive tables means that they appear opaque except under certain conditions.
* No support for FOFs, Polyobjects, or linedefs in OpenGL yet.
* All OpenGL support mostly done blind, may or may not function in practice.
If nothing else, the hard engineering problems are solved and it's just bug hammering...
Instead of figuring out where it should be every tick while it's visible, store where it'll be at the start of the map.
Also moved finish line beam into a new file, k_race.c/h, for any Race-specific code.
A few unused variables for sprint map support later too
