Graph isn't build correctly

[TamaraGunkel]

When using e.g. if-statements and interprocedural calls the flow analysis graph isn't build correctly. Setting the successors and predecessors relies on the fact that the IDs correspond to the block numbering. However, since introducing the splitting of blocks, this isn't a valid precondition anymore.
The flow analysis graph creation should not rely on the IDs anymore but be done directly during the graph creation. This should also allow us to omit nodes that do not have any operations which leads to a better performance.