cleanup tutorial startup

let update_map do the shift to center the player pos
let the map generate the submaps when needed

scent was wrong (#1324) as u.posx was out of bounds (see bounds checking in update_map), that made the scent go out of bounds.
This code calls update_map to set player pos correctly, this will also load the needed submaps into the map and generate them if needed. Therefor no need to generate them explicitly, which had a off-by-one error anyway: the tutorial room was generated on several overmap tiles, the top part was on 50,50 the bottom on 50,51. This was visible in the minimap:
![tut](https://f.cloud.github.com/assets/5095435/1581285/51e9b812-51d2-11e3-951a-d4ab8ac353c6.png)