#44 cur_int doesn't allow coordinate system as parameter

[S Mah]

According to the manual, the cur_int geometric procedure is supposed to allow a coordinate system as a surf or plane parameter. Having two coordinate systems one for the surf and one for the plane parameter probably does not make sense unless a line of infinite length can be specified. However having one coordinate system as either of the two parameters does make sense and is useful to get the intersection of a plane or surface with the XY plane of the coordinate system. However the function gives an error if either parameter is a coordinate system.