To allow the user to alternatively examine two or more windows within
a single window.
BLINK, Wndw [, T]
Wndw A vector containing the indices of the windows to blink.
T The time to wait, in seconds, between blinks. This is optional
and set to 1 if not present.
The images contained in the windows given are written to a pixmap.
The contents of the the windows are copied to a display window, in
order, until a key is struck.
Blink windows 0 and 2 with a wait time of 3 seconds
IDL> blink, [0,2], 3
Written by Michael R. Greason, STX, 2 May 1990.
Allow different size windows Wayne Landsman August, 1991
Converted to IDL V5.0 W. Landsman September 1997