If I expend a lot of time, I may be able to review the code line-by-line.

What is meant by "Correctness"?
Do you want to implement all of the OpenGL(TM) 1.0 standard? Do you
simply want code to be consitent with the comments?

Do you want to remove the "made up" define for GL_MIRRORED_REPEAT ?

That said, I feel I should point out that the code does not compile on
my machine:
render.cpp: In function `void TextureFilter(float, float, float, float,
const TextureState_t &, float25 &, float25 &, float25 &, float25 &)':
render.cpp:462: implicit declaration of function `int log2(...)'
make: *** [render.o] Error 1

I am using gcc version: 2.95.4

Wading though the (system) header files, it appears that "__USE_ISOC99"
must be defined somewhere for this to work. I am using "debian woody".
The ISOC99 standard was probably (relatively) new when my linux
distrubution was frozen.

Regards,

James Phillips