Throwable objects interact with coins

[Ordoviz]

SuperTux version: Introduced between 0.6.0 and 0.6.1-beta.1. I assume that ee86826 is to blame

Expected behavior

Throwable objects (e.g. rocks, trampoline, lanterns) do not interact with coins, checkpoints or the rotating ice balls you typically see in castles.

Actual behavior

Throwable objects bounce off coins etc. This causes throwable objects to land on a different spot than you indented or fall more slowly because they fall through a trail of coins.

Steps to reproduce actual behavior

• Throw a rock from the side on top of a coin
• Throw a rock down on a trail a of coins

[Alasdairbugs]

I think throwable objects should collect the coins, for example, throwing springs, ice cubes, blocks and more. This could allow for some more creative, and deeper gameplay.