Source zip file layout changed

[m.vanderwulp]

The 124.2.1 source zip file on sourceforge has a different layout than the one from 124.1:

- In the 124.2.1 zip, everything is in a root folder "trunk".
- In the 124.1, there is no root folder.

I prefer the 124.1 layout (without the root folder "trunk") for my work to put simutrans in the openSuse repos.

[prissi]

I just got lazy an took the github src dump as my svn is usually poisioned with a lot of extra crap. The offciial version is anyway in the svn.