display bridge also for railway=abandoned and railway=disused [PATCH]
|Internal mappaint style
bridge=* underlay is not displayed if there are no other tags. The reason is that the width of the bridge underlay is
+4 and therefore depends on the width of the line in the default layer.
railway=disused however are drawn on a separate layer because they often appear together with
highway=*. When there is no other style except the disused railway (which is not in the default layer) then the bridge cannot be displayed.
This patch fixes this the same way like it is already done for
railway=tram. The disused railway uses the default layer if there is no highway=*. Therefore bridge can be displayed.