[AD] div-by-zero.. clip3df.c

[aj <aj@xxxxxxxxxx>]

in  /allegro419/src/clip3df.c

in func()    int clip3d_f()

there is a line that reads....

	 t = (max_z - v1->z) / (v2->z - v1->z);

can someone confirm that there is no potential div-by-zero error here.
infact there are many divisions inthe function that look like they could 
cause div-by-zero.