Steampunk sewers

Patching OpenLayers.Format.SLD to allow Graphic Symbolizers

The current SVN trunk of OpenLayers.Format.SLD does not allow to write out SLD files which allow display of WellKnownName or external graphic resources. Here is a small patch to add support for 2 OpenLayers symbolizer properties: graphicName and externalGraphic. I'm to lazy to add this to the OpenLayers SVN ( and it seems the mailing - list doesn't accept mails from non-registered users...).