[Tilesathome] Disable beziercurvehinting for power=line in Osmarender

[Jannis Achstetter]

Hello,
I just noticed here ( 
http://informationfreeway.org/?lat=49.9912959686163&lon=9.088502345908955&zoom=17&layers=B000F000F 
) that powerlines are beziercurvehinted. While this is ok for streets, 
powerline usually run in straight lines (wind and hurricanes ignored). 
Can someone please exclude them from the bezier-processing (would even 
save us some ms of calculating ;)

Jannis