[patch] crossings

[Dwachs]

I rewrote the checks that are done when deciding whether a crossing is valid or can be built. The current trunk version has several problems with crossings:
1) One can build tram tracks on road/river-crossings (which exists in pak128), leading to a fatal-error.
2) If one deletes all the ways around the crossing, one can connect to the crossing from the wrong directions.
3) If one deletes the roads to a road/river crossing, one can built canals through the crossing from all sides.

Please test whether there is some unexpected behavior. Also with respect to different players.

[z9999]

This patch is very bad, this remove all things that gerw fixed.
See http://forum.simutrans.com/index.php?topic=2604.0

[Dwachs]

Thank you for testing. I updated the patch.

[z9999]

I updated the patch.

Seems to be resolved. Thank you.

[Dwachs]

in revision 2712