Skull tiles now respawn 10 seconds after crumbling

[Semphriss]

Fixes #1712

[serano01]

That changes the skull tiles, but what about the unstable tiles? They are more used after all. And if I'm not mistaken, skull tiles are unaffected by explosions.

[Semphriss]

Odd, I thought both were the same thing. Was there a reason to design both seperately at the moment of creation?

[serano01]

Skull tiles only fall when the player has been on it for a sufficient time, unstable tiles on the other hand will always fall regardless on the time.

[Semphriss]

@serano01 Done; you may test changes to see if everything is good this way. Unstable tiles now respawn too, and both skulls and unstable tiles respawn after 5 seconds.