fix mixed texgen/non-texgen with texgen modes requiring plane parameters (GL_OBJECT_L...

fix mixed texgen/non-texgen with texgen modes requiring plane parameters (GL_OBJECT_LINEAR, GL_EYE_LINEAR). This is a chip limitation, try to hack it up regardless or use a tcl fallback in some cases. Might still produce wrong results if fixed up, but so far this corrects celestia ring shadows (in multitexture mode), doom3 (arb renderer), quake4 (arb renderer and some less visible bugs in r200 renderer), and even the remaining texgenmix broken case (this is pure luck though, it is easy to construct artifical cases where it will break).