Tux with Ice power can throw bullets through 1-tile wide walls

[Semphriss]

Reproducible on any OS, on the lastest version @ master.

https://user-images.githubusercontent.com/66701383/104114612-36d48400-52fe-11eb-98c6-736807c7af95.mp4

[HybridDog]

The problem does not happen if I change the x offset in the spawn position from 0 to 8 when facing left and from 32 to 24 when facing right in this line: https://github.com/SuperTux/supertux/blob/c54014ac60f6f14fc96cadcc12f8b688268e89a2/src/object/player.cpp#L1115