Fix line-marking faces overriding other faces

[ubolonton]

This is especially useful when multiple fonts are used (e.g. for icons, proportional texts).

[purcell]

Looks good to me - thanks for this! Merging now.

[manuel-uberti]

I have this now:

Basically: marked lines are not clear anymore.

[ubolonton]

@manuel-uberti How did it previously look for you? If you want to override more properties (e.g. foreground), you can still do that by customizing the faces.

[manuel-uberti]

Before, the 3 directories marked with D had the same colour as manuel in the above screenshot.

[ubolonton]

I just created another PR to fix this.

[manuel-uberti]

Thanks!