Tunnel construction should use the same image both underground and above ground

[z9999]

r2313
FIX: tunnels now with matching roastype for current speed

This works only for above ground, in underground mode, tunnel tools still use different type of road graphics.
It should use the same image both underground and above ground.

[Dwachs]

here is a patch.

It also supports pressing ctrl-key while building. If the ctrl-key is pressed existing tunnel ways are rebuilt with the current selected one. If the key is not pressed the fastest tunnel is built / kept. In both cases straight tunnel tracks are built.