draw arbitrary curve of straight-line segments into an array
setline() will store an arbitrary curve of straight-line segments in the specified array. arglist is a list of arguments where arglist[0], arglist[2], arglist[4], etc. are referenced times, and arglist[1],[3],[5], etc., are ampltudes at those time. Straight lines will be interpolated between referenced amplitudes. An instantaneous change may be made by having successive references to the same time, with different amplitudes. The entire curve will be squeezed to length locations in array so that the referenced times are in effect proportional. n_args is the number of arguments contained in arglist. This is useful for use with table or tablei to access values in the table