- General refactoring to fit with the shared data flow implementation.
- Move CFG splitting logic into `ControlFlowReachability.qll`.
- Replace `isAdditionalFlowStepIntoCall()` with `TaintedParameterNode`.
- Redefine `ReturnNode` to be the actual values that are returned, which should
yield better path information.
- No longer consider overrides in CIL calls.