[demo] Bare update to use the new AdgPath/AdgStroke APIs
[demo] Bare update to use the new AdgPath/AdgStroke APIs

The arc primitive is not working properly: investigation needed.
Some advanced path manipulation, such as reversing a path, mirroring
and joining two paths, are missing but their implementation should
now be straight forward.

At the end, the new updates are working better than I was expecting.

ntd/adg,ntd/adg