shiny/driver/windriver: cleanup documentation and some code

Remove outdated documentation.

Add some references to articles demonstrating how
to create GUI on Windows.

Also change mkbitmap to accept image.Point.

Change-Id: I2170047262d2ee1b0fab61b4d356da4c7f6153f4
Reviewed-on: https://go-review.googlesource.com/22913
Reviewed-by: Nigel Tao <nigeltao@golang.org>
5 files changed