[sk-develop] Compiler bugs are fixed

[Martin K. <ma....@we...>]

The compiler bugs are fixed now. The project is compilable again.
I started to add docstrings to the SKVideo module. But I'm not really
happy with the result. Maybe this was a bad idea.
The docstrings are equal to the SDL documentation entries. Except some
changed names and parts which looked unnecessary.

The problem is, that some docstrings are so big, that they make the
definition module unreadable.

Maybe it's better to keep the documentation separate from the code. 
But you can use this docstrings as basis for the documentation.
Maybe you have an idea.