Fixed Knuckles being able to climb in space in OpenGL.

To understand: look at AjustSegs(void) in hw_bsp.c. It reallocates the vetex_t pointers for lines as POLYVERTEX_T pointers, and of COURSE things are gonna get wacky when you're casting pointers.

I dunno how resilient the FLOAT_TO_FIXED solution is or whether it'll be netgame compatible (yayyy float precision loss) but it's not like our builds are netgame compatible with themselves