Football/tenis/basketball pitch lines.

Stolen Christian Quest's code from the osmfr style at
https://github.com/cquest/osmfr-cartocss/, adapted to be a little
more flexible and simpler.  At low zoom levels, due to low contrasts
on football pitches, the lines are invisible though.  The SVGs were
copied as-is.

Results can be compared at
http://a.tile.openstreetmap.fr/osmfr/17/73180/43167.png or
http://a.tile.openstreetmap.fr/osmfr/17/73179/43176.png