(svg) maker halos

[StyXman]

Currently mapnik allows setting marker color (fill) and outline (stroke) when the marker is an SVG file. I would like to also have halos, which in my head "should be easily implementable with the same code that does stroke", although of course I have not a single clue how even SVG rendering is implemented.

Halos allow icons to stand out from complex backgrounds independently of other techniques like contrast.