Function: plotinit
Class: highlevel
Section: graphic
C-Name: initrect_gen
Prototype: vLD0,G,D0,G,D0,L,
Help: plotinit(w,{x=0},{y=0},{flag=0}): initialize rectwindow w to size x,y.
 If flag!=0, x and y express fractions of the size of the current output
 device. x=0 or y=0 means use the full size of the device

