Rather than displaying the stock red "Tk" icon in our window
title bars and on the task bar we now show a Git specific logo.
This is Henrik Nyh's logo that we also use in the startup wizard,
scaled to a 16x16 image for Windows task bar usage with a proper
transparent background.
Signed-off-by: Shawn O. Pearce <shawn.o.pearce@bankofamerica.com>
