Game is very unstable at the moment

[Ves]

Since the last week or so, the game has been very unstable for me. I get crash to desktop whenever I "stress" the game, ie if I am messing with trains and pressing fast forward.

I think I have managed to capture an occasion when it happens:

* Load savegame (swedish pakset): http://simutrans-germany.com/files/upload/Track_circuit_block_issues_-_TimeTel-Abso-Trackcirc_2.sve
* press "Fast forward"
* Follow the two trains when they start their trip.
* When the first train has arrived to the next station and the second train gets stuck at the last track circuit block signal, the game freezes.

[jamespetts]

I think that this is caused by thread deadlocks: it seems that a change that I implemented to try to reduce thread deadlocks has actually made them more common. I have now reverted this; would you be able to re-test? I should be grateful.

[Ves]

The game seems much more stable now!