[Coco] VCC Update

[James Ross]

Bill Pierce wrote:
> If James can come up with something that works, I would gladly merge his work into the project.

First non-trivial enhancement is working! Keep the Aspect Ratio of the CoCo screen in a Window.

A couple of screen shots

http://jamesross.biz/images/DeleteLater1.png
http://jamesross.biz/images/DeleteLater2.png

And Luis Fernández has well!! 

http://jamesross.biz/images/DeleteLater3.png

Give me more time before I ask for a Pull Request back into the upstream. I want to do a few more updates AND see if I can make it compile/build w/ the latest VS (13/15/17) as well as MinGW-x64 ... that way, anyone can build and test (and participate, if they want to).  

James