1.) I have just checked in my changes to the tdfx-2-1-branch to implement
GL_EXT_texture_env_combine. I am going to move it to tdfx-3-0-0-branch
tomorrow morning, if that branch is not superceded by yet another
rewrite during the night.
2.) GL_EXT_texture_compression_s3tc would be essentially trivial to implement,
if we (3Dfx Interactive) licensed the S3 texture compression patent.
3.) I don't know anything about GL_EXT_secondary_color, except that the
3Dfx Windows driver does not export it.