Follow-on bugs

[Laurent Bourgès]

Hi again,

As I wanted to use double precision for long, I ported main marlinFX
classes using a tricky sed scripts... fixed the 'D' pipeline and it seems
already working well.

The 2 mentioned bugs are then fixed + the performance ob DemoFX / GUIMark
(webview) seems the same as the hot spot is in scanline processing +
coverage / mask processing, not in the dasher or stroker parts.

This first prototype is promising and it only took me few hours...

However, subdiving large curves is still an interesting option to preserve
quality / accuracy even with double precision as mentioned in my previous
email.

Laurent

> PS: anyway I will later try using doubles instead of floats in Marlin,
but it will time consuming, so let's postpone such task.