VCreateImageSubwindow - creates a subwindow of the image window.
  VCreateImageSubwindow(win, xloc, yloc, width, height)
  Window *win;                          /*RETURN*/
  int xloc, yloc;
  int width, height;
  VCreateImageSubwindow creates a subwindow of the image window. The
width, height and the location of the window can be specified.
VCreateImageSubwindow returns the ID of the created window and updates
the WINS_ID.COM file. The maximum number of subwindows that can be
created in 3DVIEWNIX is defined by MAX_SUBWINS (see 3DVIEWNIX.PAR).
Return Value
  0 - work successfully.
  3 - write error.
  239 - exceeds the maximum number of subwindows (MAX_SUBWINS) under the
        image window.
  win - the window ID of the window that is created.
  xloc, yloc - the x and y coordinates of the upper-left pixel of the new
        window relative to the origin of the parent (image window).
  width, height - the width and height, in pixels, of the window.
Side Effects
Entry Conditions
  If win is NULL, or xloc, yloc, width, or height is invalid, or
VCreateWindows is not called earlier, VCreateImageSubwindow prints an 
error message to the standard error stream, produces a core dump
file and exits from the current process.
Related Functions
VDestroyImageSubwindow, VGetImageSubwindows, VGetWindowInformation.