[fix] Bridges with tram and road

[gerw]

If you build a bridge on a tile, where road and tram is built, the ribis aren't checked correctly. Furthermore you can build a track bridge on a tile containing a road (See appended screens).

The patch will fix both issues.

[gerw]

I noticed, that I've missed one case in my last patch: You can build a track/tram bridge, which ends on a tile with a road. Patch attached.