Support inner/outer demarcation of guard rail.

Position of triangles on inner guard rail side (inner surface is smooth).
Direction of triangles points usual to highway.

https://wiki.openstreetmap.org/wiki/Tag:barrier%3Dguard_rail

(minor pit: user own svg of guard_rail)

--- a/resources/styles/standard/elemstyles.mapcss
+++ b/resources/styles/standardelemstyles.mapcss
@@ -441,6 +441,7 @@
     repeat-image-align: top;
     repeat-image-offset: 0.5;
 }
+way[barrier=guard_rail],
 way[barrier=kerb] {
     repeat-image: "presets/barrier/kerb_pattern.svg";
     repeat-image-align: top;