Fixes walk aborting prematurely

when we still have enough TUs but destination is tile after closed ufo
door.

Ashura checks she has enough tu get through a door
![screen000](https://f.cloud.github.com/assets/1824834/1844482/70db63f0-752d-11e3-9225-cfab365f7396.png)

... she confidently proceeds
![screen001](https://f.cloud.github.com/assets/1824834/1844486/847ff51a-752d-11e3-80c9-5f30dae6b12a.png)

... "What the!?", says our confused hero.
![screen002](https://f.cloud.github.com/assets/1824834/1844487/a1b2f6b4-752d-11e3-99ec-1ebb5eba7285.png)

The solution I propose fixes this by charging the tu cost for door opening up to the first frame of animation, thereafter the door is effectively open so it's no charge.  This does fix the problem, but mysteriously only part of the time.  For consistency I had to ensure the animation advanced so that the fix worked all of the time.