Fix pathing mismatches between different path finding algorithms

[Kenny Long]

This ticket was created as a result of ticket #829. Units were getting stuck because of differences between the long and short pathfinder obstacle detection thresholds. A fix/hack was put into CCmpUnitMotion to compensate for this difference. This fixed the units getting stuck problem in most cases.

Now we need to make the long and short path finders agree about passable/impassable more closely so that we get better paths and have less chance of getting stuck.

The problem is described in detail here: http://www.wildfiregames.com/forum/index.php?showtopic=14883

Philip describes two possible solutions in the forum post above. We need to implement both of these and see which one plays the best and causes the least amount of code friction.

[Martin Nissen]

Playing Alpha 7 I have noticed several times, that 2 women often get obstructed by each other instead of passing around. It looks like they are taking the same path, but in opposite directions and then choose the same path trying to get around. Sometimes it resolves it self after 5-10 path changes. Other times it keeps on.

Sounds related...

[historic_bruno]

I'm going to close this as a duplicate of #1756 and #1942 (now that we know it can't be fixed without a complete rewrite), and make sure those tickets are clear about this problem.